Fix repeated cumflation hediff creation on missing genitals

[NovSugarMan]

Summary

• Query the existing cumflation hediff when evaluating the auto-deflate condition.
• Avoid creating an empty hediff as a side effect of a recurring AI condition.
• Prevent repeated attempts to attach the hediff to a missing genitals body part.

Rationale

ThinkNode_ConditionalCumflationSeverity.Satisfied only needs to determine whether an existing cumflation hediff exceeds AutoDeflateMinSeverity.

Calling GetOrCreateCumflationHediff creates a zero-severity hediff when none exists. If the pawn's genitals body part is missing, RimWorld rejects that hediff and the recurring think-tree evaluation retries the operation, repeatedly logging:

Tried to add health diff to missing part BodyPartRecord(Genitals parts.Count=0)

Using GetFirstHediffOfDef preserves the normal behavior: actual cumflation still creates the hediff through CumflatePawn, while the AI condition only reads it.

Testing

• Built the RimWorld 1.6 project successfully.
• Confirmed normal cumflation still creates the hediff.
• Confirmed pawns with a missing genitals body part no longer trigger the recurring error.

This PR intentionally targets RimWorld 1.6 only because that is the version tested locally.