fix(Core/Spell): Reset insignia spell target when it is deleted. (#21437)

src/server/game/Spells/SpellEffects.cpp

@@ -5586,6 +5586,10 @@ void Spell::EffectSkinPlayerCorpse(SpellEffIndex /*effIndex*/)
         return;
 
     unitTarget->ToPlayer()->RemovedInsignia(m_caster->ToPlayer());
+
+    // We have a corpse object as the target.
+    // This target was deleted in RemovedInsignia() -> ConvertCorpseToBones().
+    m_targets.RemoveObjectTarget();
 }
 
 void Spell::EffectStealBeneficialBuff(SpellEffIndex effIndex)