SurfaceView: Fix null check on RemoteAccessibilityController

ImporantForAccessibility can be called from the View constructor
in which case we may not have initialized RemoteAccessibilityController
yet.

Bug: 171015133
Test: Existing tests pass. Repro from bug.
Change-Id: Iedc29a9d4270ebe600648d6ce5e17c864a662396
1 file changed