Mass Mothball Dialog: Fixing IndexOutOfBoundsException with no techs for a unit type

[Windchild292]

This fixes a bug raised on Discord.

[codecov]

Codecov Report

Merging #2744 (f9db934) into master (d2c6f3e) will increase coverage by 0.00%.
The diff coverage is 0.00%.

@@            Coverage Diff            @@
##             master    #2744   +/-   ##
=========================================
  Coverage     10.60%   10.60%           
- Complexity     3851     3855    +4     
=========================================
  Files           717      717           
  Lines         99772    99774    +2     
  Branches      16402    16403    +1     
=========================================
+ Hits          10582    10586    +4     
- Misses        87810    87811    +1     
+ Partials       1380     1377    -3     

Impacted Files	Coverage Δ
MekHQ/src/mekhq/gui/dialog/MassMothballDialog.java	0.00% <0.00%> (ø)
...ekHQ/src/mekhq/campaign/market/ContractMarket.java	58.95% <0.00%> (+0.20%)	⬆️
MekHQ/src/mekhq/campaign/universe/Faction.java	66.66% <0.00%> (+0.65%)	⬆️
.../mekhq/campaign/mission/enums/AtBContractType.java	13.28% <0.00%> (+0.69%)	⬆️

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