Do not generate thumbnails in gphoto2://

Submitted by Khazar

Assigned to Jannis Pohlmann

Link to original bug (#11344)

Description

Steps to reproduce:

1. Disable display of thumbnail.
2. Plug in a digital camera device.
3. Access to gphoto2://[usb:001,011]/DCIM/
4. Thunar lets Tumbler to generate thumbnails.

Version: 1.6.3