问题描述：
安装之后显示
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报错内容：
Less_Exception_Compiler thrown with message “.tag-label is undefined in /var/www/html/flarum/vendor/flarum/mentions/less/forum.less”
Stacktrace:
#60 Less_Exception_Compiler in /var/www/html/flarum/vendor/wikimedia/less.php/lib/Less/Tree/Mixin/Call.php:148
#59 Less_Tree_Mixin_Call:compile in /var/www/html/flarum/vendor/wikimedia/less.php/lib/Less/Tree/Ruleset.php:147
#58 Less_Tree_Ruleset:EvalMixinCalls in /var/www/html/flarum/vendor/wikimedia/less.php/lib/Less/Tree/Ruleset.php:90
#57 Less_Tree_Ruleset:compile in /var/www/html/flarum/vendor/wikimedia/less.php/lib/Less/Tree/Ruleset.php:95
#56 Less_Tree_Ruleset:compile in /var/www/html/flarum/vendor/wikimedia/less.php/lib/Less/Tree/Ruleset.php:95
#55 Less_Tree_Ruleset:compile in /var/www/html/flarum/vendor/wikimedia/less.php/lib/Less/Parser.php:181
#54 Less_Parser:getCss in /var/www/html/flarum/vendor/flarum/core/src/Frontend/Compiler/LessCompiler.php:116
#53 Flarum\Frontend\Compiler\LessCompiler:compile in /var/www/html/flarum/vendor/flarum/core/src/Frontend/Compiler/RevisionCompiler.php:138
#52 Flarum\Frontend\Compiler\RevisionCompiler:save in /var/www/html/flarum/vendor/flarum/core/src/Frontend/Compiler/RevisionCompiler.php:76
#51 Flarum\Frontend\Compiler\RevisionCompiler:commit in /var/www/html/flarum/vendor/flarum/core/src/Frontend/Content/Assets.php:105
#50 Flarum\Frontend\Content\Assets:forceCommit in /var/www/html/flarum/vendor/flarum/core/src/Frontend/Content/Assets.php:63
#49 Flarum\Frontend\Content\Assets:__invoke in /var/www/html/flarum/vendor/flarum/core/src/Frontend/Frontend.php:62
#48 Flarum\Frontend\Frontend:populate in /var/www/html/flarum/vendor/flarum/core/src/Frontend/Frontend.php:54
#47 Flarum\Frontend\Frontend:document in /var/www/html/flarum/vendor/flarum/core/src/Frontend/Controller.php:32
#46 Flarum\Frontend\Controller:handle in /var/www/html/flarum/vendor/flarum/core/src/Http/RouteHandlerFactory.php:41
#45 Flarum\Http\RouteHandlerFactory:Flarum\Http{closure} in /var/www/html/flarum/vendor/flarum/core/src/Http/Middleware/ExecuteRoute.php:27
#44 Flarum\Http\Middleware\ExecuteRoute:process in /var/www/html/flarum/vendor/laminas/laminas-stratigility/src/Next.php:49
#43 Laminas\Stratigility\Next:handle in /var/www/html/flarum/vendor/flarum/core/src/Http/Middleware/ContentTypeOptionsHeader.php:21
#42 Flarum\Http\Middleware\ContentTypeOptionsHeader:process in /var/www/html/flarum/vendor/laminas/laminas-stratigility/src/Next.php:49
#41 Laminas\Stratigility\Next:handle in /var/www/html/flarum/vendor/flarum/core/src/Http/Middleware/ReferrerPolicyHeader.php:30
#40 Flarum\Http\Middleware\ReferrerPolicyHeader:process in /var/www/html/flarum/vendor/laminas/laminas-stratigility/src/Next.php:49
#39 Laminas\Stratigility\Next:handle in /var/www/html/flarum/vendor/flarum/core/src/Http/Middleware/FlarumPromotionHeader.php:30
#38 Flarum\Http\Middleware\FlarumPromotionHeader:process in /var/www/html/flarum/vendor/laminas/laminas-stratigility/src/Next.php:49
#37 Laminas\Stratigility\Next:handle in /var/www/html/flarum/vendor/flarum/core/src/Http/Middleware/ShareErrorsFromSession.php:57
#36 Flarum\Http\Middleware\ShareErrorsFromSession:process in /var/www/html/flarum/vendor/laminas/laminas-stratigility/src/Next.php:49
#35 Laminas\Stratigility\Next:handle in /var/www/html/flarum/vendor/flarum/core/src/Http/Middleware/CheckCsrfToken.php:36
#34 Flarum\Http\Middleware\CheckCsrfToken:process in /var/www/html/flarum/vendor/laminas/laminas-stratigility/src/Next.php:49
#33 Laminas\Stratigility\Next:handle in /var/www/html/flarum/vendor/flarum/core/src/Http/Middleware/ResolveRoute.php:69
#32 Flarum\Http\Middleware\ResolveRoute:process in /var/www/html/flarum/vendor/laminas/laminas-stratigility/src/Next.php:49
#31 Laminas\Stratigility\Next:handle in /var/www/html/flarum/vendor/flarum/core/src/Http/Middleware/SetLocale.php:51
#30 Flarum\Http\Middleware\SetLocale:process in /var/www/html/flarum/vendor/laminas/laminas-stratigility/src/Next.php:49
#29 Laminas\Stratigility\Next:handle in /var/www/html/flarum/vendor/flarum/core/src/Http/Middleware/AuthenticateWithSession.php:31
#28 Flarum\Http\Middleware\AuthenticateWithSession:process in /var/www/html/flarum/vendor/laminas/laminas-stratigility/src/Next.php:49
#27 Laminas\Stratigility\Next:handle in /var/www/html/flarum/vendor/flarum/core/src/Http/Middleware/RememberFromCookie.php:52
#26 Flarum\Http\Middleware\RememberFromCookie:process in /var/www/html/flarum/vendor/laminas/laminas-stratigility/src/Next.php:49
#25 Laminas\Stratigility\Next:handle in /var/www/html/flarum/vendor/flarum/core/src/Http/Middleware/StartSession.php:61
#24 Flarum\Http\Middleware\StartSession:process in /var/www/html/flarum/vendor/laminas/laminas-stratigility/src/Next.php:49
#23 Laminas\Stratigility\Next:handle in /var/www/html/flarum/vendor/flarum/core/src/Http/Middleware/CollectGarbage.php:46
#22 Flarum\Http\Middleware\CollectGarbage:process in /var/www/html/flarum/vendor/laminas/laminas-stratigility/src/Next.php:49
#21 Laminas\Stratigility\Next:handle in /var/www/html/flarum/vendor/flarum/core/src/Http/Middleware/ParseJsonBody.php:28
#20 Flarum\Http\Middleware\ParseJsonBody:process in /var/www/html/flarum/vendor/laminas/laminas-stratigility/src/Next.php:49
#19 Laminas\Stratigility\Next:handle in /var/www/html/flarum/vendor/flarum/core/src/Http/Middleware/HandleErrors.php:57
#18 Flarum\Http\Middleware\HandleErrors:process in /var/www/html/flarum/vendor/laminas/laminas-stratigility/src/Next.php:49
#17 Laminas\Stratigility\Next:handle in /var/www/html/flarum/vendor/flarum/core/src/Http/Middleware/InjectActorReference.php:25
#16 Flarum\Http\Middleware\InjectActorReference:process in /var/www/html/flarum/vendor/laminas/laminas-stratigility/src/Next.php:49
#15 Laminas\Stratigility\Next:handle in /var/www/html/flarum/vendor/laminas/laminas-stratigility/src/MiddlewarePipe.php:75
#14 Laminas\Stratigility\MiddlewarePipe:process in /var/www/html/flarum/vendor/middlewares/request-handler/src/RequestHandler.php:84
#13 Middlewares\RequestHandler:process in /var/www/html/flarum/vendor/laminas/laminas-stratigility/src/Next.php:49
#12 Laminas\Stratigility\Next:handle in /var/www/html/flarum/vendor/middlewares/base-path-router/src/BasePathRouter.php:101
#11 Middlewares\BasePathRouter:process in /var/www/html/flarum/vendor/laminas/laminas-stratigility/src/Next.php:49
#10 Laminas\Stratigility\Next:handle in /var/www/html/flarum/vendor/laminas/laminas-stratigility/src/Middleware/OriginalMessages.php:36
#9 Laminas\Stratigility\Middleware\OriginalMessages:process in /var/www/html/flarum/vendor/laminas/laminas-stratigility/src/Next.php:49
#8 Laminas\Stratigility\Next:handle in /var/www/html/flarum/vendor/middlewares/base-path/src/BasePath.php:73
#7 Middlewares\BasePath:process in /var/www/html/flarum/vendor/laminas/laminas-stratigility/src/Next.php:49
#6 Laminas\Stratigility\Next:handle in /var/www/html/flarum/vendor/flarum/core/src/Http/Middleware/ProcessIp.php:24
#5 Flarum\Http\Middleware\ProcessIp:process in /var/www/html/flarum/vendor/laminas/laminas-stratigility/src/Next.php:49
#4 Laminas\Stratigility\Next:handle in /var/www/html/flarum/vendor/laminas/laminas-stratigility/src/MiddlewarePipe.php:75
#3 Laminas\Stratigility\MiddlewarePipe:process in /var/www/html/flarum/vendor/laminas/laminas-stratigility/src/MiddlewarePipe.php:64
#2 Laminas\Stratigility\MiddlewarePipe:handle in /var/www/html/flarum/vendor/laminas/laminas-httphandlerrunner/src/RequestHandlerRunner.php:96
#1 Laminas\HttpHandlerRunner\RequestHandlerRunner:run in /var/www/html/flarum/vendor/flarum/core/src/Http/Server.php:45
#0 Flarum\Http\Server:listen in /var/www/html/flarum/public/index.php:26
