Grouping of images can add non-selected photos

Describe the bug

In group mode, when adding images to a group, non-selected photos can be added to a group.

Steps to reproduce

1. Enter group mode
2. Select images a.jpg and a.raw - top level message says that 2 images are selected
3. Press Ctrl-G to group images - group is created as expected
4. Select images b.jpg, b.raw, and b-1.jpg - top level message says that 3 images are selected; note that b-1.jpg is a distinct file on disk.
5. Press Ctrl-G to group images - group of 5 images is created and consists of a.* and b* photos
6. There is one group of images, instead of two

This might happen randomly. Seems more prevalent with hundreds of images in a roll.

Expected behavior

There should be two group of images, not one.

Logfile | Screenshot | Screencast

No response

Commit

No response

Where did you obtain darktable from?

distro packaging

darktable version

4.8.1

What OS are you using?

Linux

What is the version of your OS?

ArchLinux

Describe your system?

No response

Are you using OpenCL GPU in darktable?

I dont know

If yes, what is the GPU card and driver?

No response

Please provide additional context if applicable. You can attach files too, but might need to rename to .txt or .zip

No response

Start by reproducing the grouping sequence in darktable 4.8.1: group a.jpg with a.raw, then b.jpg, b.raw, and b-1.jpg, especially with a large roll. Trace the group-mode selection and Ctrl-G entry point to find why earlier photos remain included. Done means the same steps create two groups containing only the currently selected images.