Dialogs: Window icon is missing sometimes

Version information

Thunar 4.19.3 on Xubuntu 24.10

Thunar 4.18.10 on Fedora 40 Xfce

Steps to reproduce

1. In xfwm4, use "Default" window theme
2. In xfwm4, make sure the "Menu" button is active
3. In Thunar, Right Click on file or folder
4. Select "Properties"

Other dialogs affected: "Configure custom actions" "Configure Toolbar" "Select by pattern" "Create Folder" "Rename"

Current behavior

The window icon is missing in many themes. From what I can tell, Thunar seems to look for an icon named Thunar in the icon theme. If not found, a generic window icon is used (I believe from xfwm).

Expected outcome

It should use the newer named app icon, org.xfce.thunar, so that it can fall back to the Thunar-provided hicolor icon if an icon theme doesn't provide it. Another solution, maybe the icon/thumbnail next to "Name" in the dialog could be used. (or possibly document-properties, the icon that Right Click > Properties uses)

Additional information

This shows the dialog uses the Thunar icon when available and not org.xfce.thunar.

Maybe here needs to be changed? It's a simple and trivial thing I can check later but I currently don't have the build tools installed, or the time. I can come back and try when I'm able (if no one else checks it out before then).