Fix potential NULL dereference in Visualizer effect am: 874f9e0b8e am: f060479b9a am: bcc7230bb9 am: f4a63f6765 am: ecfd198cda am: bae68c9e15 am: d36ebed01e am: 1b963dc33c am: b4842ae2d4 am: 59f22c99fe am: 7fc03ff680
am: 7b8a3a9fa8

Change-Id: Ic0fca89e54d04ce8f5cfe7a3d02a5dd2bc3b4d37