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

Change-Id: I70bcbef181d3d6acc5cd53c43e792b4d7068ad2a