ImagePicker: Uploading new image fails if user doesn't first select gallery folder

1. Start editing any document with a xinha field.
2. Select the xinha field and press 'Insert/ Modify image'
3. The Image Picker dialog opens, on top is the 'upload new' functionality, on the left is the tree structure showing the gallery folder and contents
4. Without selecting a folder on the left, try uploading a new image. This fails with: ERROR [org.hippoecm.frontend.plugins.xinha.dialog.images.ImageBrowserDialog$7.onSubmit():302] no matching property definition found for

filename

Everything works properly if you first select a gallery folder.
This is not occurring in 7.7, only in 7.6. I couldn't find any info that it has been fixed though. Could it be my installation only? Is there any setting about this?