1.9.3: Big files are not deleted if preview is not generated

[moropus]

XnView: MP 1.9.3 - 64 bit
OS: Windows 10 64bit

Big files are not deleted in browser if preview is being generated. This slows down the processing of images.

To reproduce:
1. Have a couple of huge files in folder, say 200 mb tiffs on hdd (works with smaller files and faster storages, but you need to be much faster)
2. Open Browser
3. Select files
4. While the preview is not yet generated, delete files
Actual behaviour (bug):
- One file is not deleted
Expected behaviour:
- All files are deleted, the making of preview is canceled

On the attached video you can see the bug reproduction. Then I copy the same files to the folder and delete them after the preview got visible, and the files are deleted after.

[xnview]

right if current image is in loading