Polygons packing may not pack an image regions correctly if it is referenced by some mesh attachments

[misaki-eymard]

Description:
If there are multiple mesh attachments that reference the same image, and if there are multiple mesh attachments, e.g., if any of them are duplicated, there is a problem with Polygons packing where some regions are not packed correctly.

Expected behavior:
Even if there are multiple mesh attachments that reference the same image, and even if there are multiple mesh attachments, e.g., if any of them are duplicated, all regions will be packed correctly.

Steps to reproduce:

1. Download the attached .zip file: Polygons packing may not pack an image regions correctly if it is referenced by some mesh attachments.zip
2. Open the Spine project contained in the unpacked .zip file using Spine 4.2.36. Here's what the skeleton included in that project looks like:
   
   Make sure that the light blue and red circle mesh attachments refer to the same image.
3. First, perform a texture pack in this state to confirm that it packs correctly. Open the texture packer settings and load the json.pack.json contained in the .zip file to pack the textures. After loading, the pack settings should look something like this:
   
4. Run the pack and check the output PNG. It should look something like this:
   
5. Select slot A2 and duplicate it.
   
6. Pack the texture with the same settings as you did in step 4.
7. If you look at the output texture, you will see that the red circle has disappeared:
   

If you duplicate A1 instead of A2 in step 5 and pack the texture, you will see that this time only the red circle is output and not the light blue circle:

Also, if you duplicate both A2 and A1, you will get a blank texture:

The versions of Spine that can reproduce this issue:
Spine 4.2.36

This issue was reported in the following thread on the forum:
https://esotericsoftware.com/forum/d/27167-%E8%BF%99%E6%98%AF%E5%A4%9A%E8%BE%B9%E5%BD%A2%E6%89%93%E5%8C%85%E5%9B%BE%E9%9B%86%E7%9A%84bug%E5%90%97