论坛迁移的时候/vendor文件复制过去，然后修改了composer.json修改之后，其他插件运行良好，就只有flagrow/upload报错。移除插件，清楚缓存，重新安装插件也不行了。
报错debug代码：
POST http://www.longhuke.com/api/flagrow/upload
{
"errors": [
{
"code": 500,
"title": "Internal server error",
"detail": "exception 'Intervention\Image\Exception\NotReadableException' with message 'Image source not readable' in /var/www/html/vendor/intervention/image/src/Intervention/Image/AbstractDecoder.php:335\nStack trace:\n#0 /var/www/html/vendor/intervention/image/src/Intervention/Image/AbstractDriver.php(64): Intervention\Image\AbstractDecoder->init('/var/www/html/s...')\n#1 /var/www/html/vendor/intervention/image/src/Intervention/Image/Gd/Commands/InsertCommand.php(21): Intervention\Image\AbstractDriver->init('/var/www/html/s...')\n#2 /var/www/html/vendor/intervention/image/src/Intervention/Image/AbstractDriver.php(92): Intervention\Image\Gd\Commands\InsertCommand->execute(Object(Intervention\Image\Image))\n#3 /var/www/html/vendor/intervention/image/src/Intervention/Image/Image.php(106): Intervention\Image\AbstractDriver->executeCommand(Object(Intervention\Image\Image), 'insert', Array)\n#4 /var/www/html/vendor/flagrow/upload/src/Processors/ImageProcessor.php(81): Intervention\Image\Image->__call('insert', Array)\n#5 /var/www/html/vendor/flagrow/upload/src/Processors/ImageProcessor.php(81): Intervention\Image\Image->insert('/var/www/html/s...', 'bottom-right')\n#6 /var/www/html/vendor/flagrow/upload/src/Processors/ImageProcessor.php(54): Flagrow\Upload\Processors\ImageProcessor->watermark(Object(Intervention\Image\Image))\n#7 /var/www/html/vendor/flagrow/upload/src/Listeners/ProcessesImages.php(33): Flagrow\Upload\Processors\ImageProcessor->process(Object(Flagrow\Upload\File), Object(Symfony\Component\HttpFoundation\File\UploadedFile))\n#8 [internal function]: Flagrow\Upload\Listeners\ProcessesImages-