Fix 4061: Failure to load older Campaign save

[Sleet01]

Issues for the reported campaign are twofold:

1. 3 Persons use a systemId that has changed in 0.49.19, causing the planetId lookup to fail.
2. At least one infantry unit has a quirk or ability that grants it BAP equivalent sensors, but no actual sensors; this causes a new-to-0.49.19 cleanup step to fail on loading the unit(s).

Fix is to add try/catch and better conditionals around the failing code blocks.

Testing:

• Ran all three projects' unit tests
• Added unit test for clearGameData() with affected Infantry unit instance.
• Loaded OP's previously-failing campaign save successfully.

Close #4061