Exception guards for report search fields

[SJuliez]

Fixes exceptions thrown in comboXYZ.setSelectedIndex(0) when the search combos in the report display are empty (happened to me when calling up the report at the end of a game).

[codecov]

Codecov Report

Base: 22.99% // Head: 23.00% // Increases project coverage by +0.00% 🎉

Coverage data is based on head (bb35df7) compared to base (03402de).
Patch coverage: 1.67% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##             master    #4047    +/-   ##
==========================================
  Coverage     22.99%   23.00%            
  Complexity     4813     4813            
==========================================
  Files          2263     2264     +1     
  Lines        249065   249498   +433     
  Branches      46253    46325    +72     
==========================================
+ Hits          57281    57398   +117     
- Misses       190325   190641   +316     
  Partials       1459     1459            

Impacted Files	Coverage Δ
megamek/src/megamek/Version.java	29.54% <0.00%> (-2.17%)	⬇️
...egamek/src/megamek/client/ui/swing/MegaMekGUI.java	0.00% <0.00%> (ø)
...src/megamek/client/ui/swing/MiniReportDisplay.java	0.00% <0.00%> (ø)
megamek/src/megamek/common/EquipmentType.java	34.46% <0.00%> (+0.44%)	⬆️
...ommon/alphaStrike/conversion/ASLocationMapper.java	0.00% <ø> (ø)
...haStrike/conversion/ASSpecialAbilityConverter.java	0.00% <0.00%> (ø)
...c/megamek/common/preference/ClientPreferences.java	31.61% <ø> (ø)
...egamek/src/megamek/common/weapons/ACAPHandler.java	0.00% <0.00%> (ø)
.../src/megamek/common/weapons/AmmoWeaponHandler.java	0.00% <0.00%> (ø)
...k/src/megamek/common/weapons/BayWeaponHandler.java	0.00% <0.00%> (ø)
... and 22 more

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

☔ View full report at Codecov.
📢 Do you have feedback about the report comment? Let us know in this issue.