Handled StratCon Scenario Placement Failure when All Coordinates Occupied

[IllianiCBT]

Added checks to handle scenarios where facilities or objectives could not be placed because all coordinates in a StratCon track were occupied. Issued warnings and errors, and updated the getUnoccupiedCoords method to return null when placement is not possible.

It's worth noting that this is not a scenario that is likely to ever come up, because what are the chances we try to place a new scenario down on a track where every hex is occupied? In vanilla StratCon that scenario will never occur because getUnoccupiedCoords is only called at the beginning of a contract when a track is effectively empty.

I'm currently working on a secret project that will require me to place events on the StratCon map. I'm planning to use getUnoccupiedCoords, as I don't want stacked events, but that raises the chance of this exception occurring from 'none' to 'very low'. Prior to this PR, if that scenario did occur the client would end in an infinite loop.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 10.53%. Comparing base (fb6c52a) to head (c4b5af8).
Report is 32 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #5141      +/-   ##
============================================
- Coverage     10.53%   10.53%   -0.01%     
- Complexity     6041     6043       +2     
============================================
  Files           956      956              
  Lines        134253   134276      +23     
  Branches      19501    19508       +7     
============================================
+ Hits          14142    14144       +2     
- Misses       118760   118780      +20     
- Partials       1351     1352       +1     

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