石博文 22d612ef14 fix crash when drag out of preview container.
because the tracking window is unavilable.

Change-Id: I6cbdf76c7eb3eebcb628aa13496c06c4a7d4b692
2018-01-12 15:25:28 +08:00
..
2018-01-02 14:08:10 +08:00
2017-09-20 11:23:51 +08:00
2017-12-05 13:08:17 +08:00