Core/Misc: Minor optimizations (+code changes to reduce differences with 4.3.4 branch)

Core/Logging: Create new logger type "Cheat". Will be used to log all cheat attempts

src/server/game/Instances/InstanceScript.cpp

@@ -403,6 +403,8 @@ void InstanceScript::SendEncounterUnit(uint32 type, Unit* unit /*= NULL*/, uint8
         case ENCOUNTER_FRAME_ENGAGE:
         case ENCOUNTER_FRAME_DISENGAGE:
         case ENCOUNTER_FRAME_UPDATE_PRIORITY:
+            if (!unit)
+                return;
             data.append(unit->GetPackGUID());
             data << uint8(param1);
             break;