Could not load gfx file "tilesets/flags/northernireland

[jwrober]

Describe the bug

[critical] freeciv21-client - Could not load gfx file "tilesets/flags/northernireland-large".
[critical] freeciv21-client - Could not load gfx file "tilesets/flags/northernireland-shield-large".

To Reproduce Steps to reproduce the behavior:

1. Start client from command-line
2. See error

Expected behavior Tileset graphics work

Screenshots N/A

Platform and version (please complete the following information):

• OS: Linux
• Freeciv21 version: 3.1-beta.1
• Ruleset/Longturn game (if applicable): N/A

Additional context Found while testing PR 2288, but don't think its related.