Fix broken of running animation - Running animation is stop automatically after a certain time. - It is 300ms according MBScene._updateUI(). - It is caused by notification of changing DOM tree. The notification handlers would call MBScene.updateUI() to update framelines and buttons. - MBScene.updateUI() would call MBScene.show() after 300ms, MBScene.show() calls MBScene.parseScene() in turn. - MBScene.parseScene() would remove duplicate group that is using by code of running animation, MBScene.doRunNext(). It make running animation stop. - fixed by setting MBScene.lockui when a running animation is started or stoped.

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