Investigating an allied city prevents one from activating own units inside

[lmoureaux]

Describe the bug After investigating an allied city, the city dialog will always pop up, but the unit list is inactive. This prevents one from activating one's own units.

To Reproduce Steps to reproduce the behavior:

1. Move unit A to an allied city
2. Investigate that city with a diplomat
3. The city dialog pops up
4. Try to activate unit A
5. Fail to do so until you reconnect

Expected behavior One can activate one's own units from the city dialog.

Platform and version (please complete the following information):

• OS: n/a
• Freeciv21 version: master
• Ruleset/Longturn game (if applicable): LT82