Core/AI: Fix uninitialized values in SMART_ACTION_CREATE_TIMED_EVENT action

Proper initialize POD struct members to 0 in SMART_ACTION_CREATE_TIMED_EVENT action type.

Valgrind log:
 Conditional jump or move depends on uninitialised value(s)
   at : SmartScript::UpdateTimer(SmartScriptHolder&, unsigned int) (SmartScript.cpp:3086)
   by : SmartScript::OnUpdate(unsigned int) (SmartScript.cpp:3176)
   by : SmartAI::UpdateAI(unsigned int) (SmartAI.cpp:335)
   by : Creature::Update(unsigned int) (Creature.cpp:542)
   by : TempSummon::Update(unsigned int) (TemporarySummon.cpp:47)

 Uninitialised value was created by a stack allocation
   at : SmartScript::ProcessAction(SmartScriptHolder&, Unit*, unsigned int, unsigned int, bool, SpellInfo const*, GameObject*) (SmartScript.cpp:143)