When I try to upload an image in a category I am getting below error.
The issue I found is that the function in the file 'vendor\magento\module-catalog\Model\ImageUploader.php'
public function saveFileToTmpDir($fileId) is called two times. One with the parameter 'image' and then with the parameter 'thumb_nail'. The error happens when it is called with the parameter 'thumb_nail'. I couldn't find where that function is getting called. It is supposed to be called from the controller 'vendor\magento\module-catalog\Controller\Adminhtml\Category\Image\Upload.php'. But when I comment out the code in the controller it is still being called. And it is supposed to be called one time with the parameter 'image'