Fix potential NULL dereference in Visualizer effect am: 874f9e0b8e am: f060479b9a am: bcc7230bb9 am: f4a63f6765 am: ecfd198cda am: bae68c9e15
am: d36ebed01e

Change-Id: Icc846170a93c7f1aa348645609f57b28e8a8c76c