Instead mark spell as delatable mark it as executed and referenced from Unit current spells array and not deleted spell in like cases.

This is solve crashs if spell deleted at caster die in result triggered spells casting chain from currently executed spell.

src/game/SpellAuras.cpp

@@ -3470,7 +3470,7 @@ void Aura::HandleAuraModSilence(bool apply, bool Real)
                 if ( state == SPELL_STATE_PREPARING || state == SPELL_STATE_CASTING )
                 {
                     currentSpell->cancel();
-                    currentSpell->SetDeletable(true);
+                    currentSpell->SetReferencedFromCurrent(false);
                     m_target->m_currentSpells[i] = NULL;
                 }
             }