Core/Misc: Fix some static analysis issues

Add some asserts and additional NULL checks as sanity checks.

src/server/scripts/Spells/spell_pet.cpp

@@ -941,6 +941,7 @@ public:
                 if (itr != pet->ToPet()->m_spells.end()) // If pet has Wild Hunt
                 {
                     SpellInfo const* spellInfo = sSpellMgr->GetSpellInfo(itr->first); // Then get the SpellProto and add the dummy effect value
+                    ASSERT(spellInfo);
                     mod += CalculatePct(1.0f, spellInfo->Effects[EFFECT_1].CalcValue());
                 }
 
@@ -971,6 +972,7 @@ public:
                 if (itr != pet->ToPet()->m_spells.end()) // If pet has Wild Hunt
                 {
                     SpellInfo const* spellInfo = sSpellMgr->GetSpellInfo(itr->first); // Then get the SpellProto and add the dummy effect value
+                    ASSERT(spellInfo);
                     mod += CalculatePct(1.0f, spellInfo->Effects[EFFECT_1].CalcValue());
                 }