Core/SAI: Fix crash in SmartScript

Fix crash in SmartScript storing WorldObject* instead of guid as targets in SmartScript::mTargetStorage , used by SMART_TARGET_STORED target type , SMART_ESCORT_TARGETS and other escort related code.
Fixes #11228 , #10157 .

Valgrind log:
 Invalid read of size 4
  at : Object::GetTypeId() const (Object.h:140)
  by : SmartScript::IsPlayer(WorldObject*) (SmartScript.h:73)
  by : SmartScript::ProcessAction(SmartScriptHolder&, Unit*, unsigned int, unsigned int, bool, SpellInfo const*, GameObject*) (SmartScript.cpp:330)
  by : SmartScript::ProcessEvent(SmartScriptHolder&, Unit*, unsigned int, unsigned int, bool, SpellInfo const*, GameObject*) (SmartScript.cpp:2662)
  by : SmartScript::ProcessAction(SmartScriptHolder&, Unit*, unsigned int, unsigned int, bool, SpellInfo const*, GameObject*) (SmartScript.cpp:2226)
  by : SmartScript::ProcessTimedAction(SmartScriptHolder&, unsigned int const&, unsigned int const&, Unit*, unsigned int, unsigned int, bool, SpellInfo const*, GameObject*) (SmartScript.cpp:2238)
  by : SmartScript::ProcessEvent(SmartScriptHolder&, Unit*, unsigned int, unsigned int, bool, SpellInfo const*, GameObject*) (SmartScript.cpp:2685)
  by : SmartScript::UpdateTimer(SmartScriptHolder&, unsigned int) (SmartScript.cpp:3198)
  by : SmartScript::OnUpdate(unsigned int) (SmartScript.cpp:3244)
  by : SmartAI::UpdateAI(unsigned int) (SmartAI.cpp:331)
  by : Creature::Update(unsigned int) (Creature.cpp:544)
  by : void Trinity::ObjectUpdater::Visit<Creature>(GridRefManager<Creature>&) (GridNotifiers.cpp:340)