Core/Movement: Prevent IdleMovementGenerator being put into MOTION_SLOT_IDLE and MOTION_SLOT_ACTIVE simultaneously

src/server/game/Entities/Creature/Creature.cpp

@@ -715,7 +715,7 @@ void Creature::Motion_Initialize()
         i_motionMaster.Initialize();
     }
     else if (m_formation->isFormed())
-        i_motionMaster.MoveIdle(MOTION_SLOT_IDLE); //wait the order of leader
+        i_motionMaster.MoveIdle(); //wait the order of leader
     else
         i_motionMaster.Initialize();
 }

src/server/game/Entities/Creature/CreatureGroups.cpp

@@ -203,7 +203,7 @@ void CreatureGroup::FormationReset(bool dismiss)
             if (dismiss)
                 itr->first->GetMotionMaster()->Initialize();
             else
-                itr->first->GetMotionMaster()->MoveIdle(MOTION_SLOT_IDLE);
+                itr->first->GetMotionMaster()->MoveIdle();
             sLog->outDebug(LOG_FILTER_UNITS, "Set %s movement for member GUID: %u", dismiss ? "default" : "idle", itr->first->GetGUIDLow());
         }
     }

src/server/game/Movement/MotionMaster.cpp

@@ -175,12 +175,11 @@ void MotionMaster::DelayedExpire()
         --i_top;
 }
 
-void MotionMaster::MoveIdle(MovementSlot slot)
+void MotionMaster::MoveIdle()
 {
-    //if (empty() || !isStatic(top()))
-    //    push(&si_idleMovement);
-    if (!isStatic(Impl[slot]))
-        Mutate(&si_idleMovement, slot);
+    //! Should be preceded by MovementExpired or Clear if there's an overlying movementgenerator active
+    if (empty() || !isStatic(top()))
+        Mutate(&si_idleMovement, MOTION_SLOT_IDLE);
 }
 
 void MotionMaster::MoveRandom(float spawndist)

src/server/game/Movement/MotionMaster.h

@@ -142,7 +142,7 @@ class MotionMaster //: private std::stack<MovementGenerator *>
                 DirectExpire(reset);
         }
 
-        void MoveIdle(MovementSlot slot = MOTION_SLOT_ACTIVE);
+        void MoveIdle();
         void MoveTargetedHome();
         void MoveRandom(float spawndist = 0.0f);
         void MoveFollow(Unit* target, float dist, float angle, MovementSlot slot = MOTION_SLOT_ACTIVE);

src/server/game/Server/Protocol/Handlers/PetHandler.cpp

@@ -155,6 +155,7 @@ void WorldSession::HandlePetActionHelper(Unit* pet, uint64 guid1, uint16 spellid
                 case COMMAND_STAY:                          //flat=1792  //STAY
                     pet->AttackStop();
                     pet->InterruptNonMeleeSpells(false);
+                    pet->GetMotionMaster()->Clear(false);
                     pet->GetMotionMaster()->MoveIdle();
                     charmInfo->SetCommandState(COMMAND_STAY);