Core/Spells: fix a crash.

src/server/game/Spells/Spell.cpp

@@ -5464,7 +5464,8 @@ SpellCastResult Spell::CheckPetCast(Unit* target)
 
     Unit* _target = m_targets.GetUnitTarget();
 
-        if (_target)                                         //for target dead/target not valid
+    // for target dead/target not valid
+    if (_target)
     {
         if (!_target->isAlive())
             return SPELL_FAILED_BAD_TARGETS;
@@ -5472,8 +5473,10 @@ SpellCastResult Spell::CheckPetCast(Unit* target)
         if (!IsValidSingleTargetSpell(_target))
             return SPELL_FAILED_BAD_TARGETS;
     }
+
     // cooldown
-        if (m_caster->ToCreature()->HasSpellCooldown(m_spellInfo->Id))
+    if (Unit const* creatureCaster = m_caster->ToCreature())
+        creatureCaster->HasSpellCooldown(m_spellInfo->Id))
             return SPELL_FAILED_NOT_READY;
 
     return CheckCast(true);