Null checks in manual contract generation

[DM0000]

closes #5149

Added null checks for Employer, Enemy, and Planet with matching messages.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 10.47%. Comparing base (d1b53f6) to head (d333f62).
Report is 19 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##             master    #5270    +/-   ##
==========================================
  Coverage     10.47%   10.47%            
- Complexity     6039     6049    +10     
==========================================
  Files           959      959            
  Lines        135067   135202   +135     
  Branches      19650    19674    +24     
==========================================
+ Hits          14147    14165    +18     
- Misses       119569   119686   +117     
  Partials       1351     1351            

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.