移动塔的时候碰到空塔位给一个虚影，没有资源暂时return

wangguan

2020-11-09 5d16d6e5172daf42d386baa5c09663b422f05a59

 Assets/Scripts/TowerDefense/Input/EndlessTowerDefenseKeyboardMouseInput.cs

@@ -164,6 +164,8 @@
            if ((pointer != null) && (m_GameUI.isBuilding))
            {
                m_GameUI.TryMoveGhost(pointer, false);

                m_GameUI.CheckTowerPlace(pointer);
            }
        }