Core/Misc: Fix an exploit where moving while consuming something that would fade when the player stands up would stay if the player started moving and using the effect at the same time. Thanks to @FrozenSoul and @jildor.

Fixes #6271

src/server/game/Handlers/MovementHandler.cpp

@@ -381,6 +381,9 @@ void WorldSession::HandleMovementOpcodes(WorldPacket& recvData)
 
     if (plrMover)                                            // nothing is charmed, or player charmed
     {
+        if (plrMover->IsSitState() && (movementInfo.flags & (MOVEMENTFLAG_MASK_MOVING | MOVEMENTFLAG_MASK_TURNING)))
+            plrMover->SetStandState(UNIT_STAND_STATE_STAND);
+
         plrMover->UpdateFallInformationIfNeed(movementInfo, opcode);
 
         if (movementInfo.pos.GetPositionZ() < -500.0f)