Fixes advanced sorting with modded installs, including Mk2 Expansion and SystemHeat.

[Jaheay]

• Handles duplicate and malformed part entries without breaking the sort index
• Supports wrapped and standalone sorting-variable configurations
• Resolves a minor compiler warning

AFAIK:

• Fixes Advanced Sorting Mode breaks when used alongside other mods. #30
• Fixes Fix for dictionary key exception in AdvancedSortingDataStore.OnPartLoaderLoaded #31
• Related to Issues when selecting custom category #33

[R-T-B]

This seems to work in my testing, btw. I'm going to take the burden on here since no one seems to be working on this mod otherwise from KSPModStewards, and issue a hotfix with this code. Blame me.