accelbubble: avoid updating position if NaN.

Invalid sensor data is NaN, and should be ignored.

Change-Id: I6436bdd494b3d167121bd8ee80f81c031e60743e
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
accelbubble: disable rotation on iOS

Change-Id: Ia3f6bdd494b3d167121bd8ee80f81c031a81f45a
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
ios: skip accelerometer, gyroscope and magnetomenter updates if NaN

Change-Id: I7becfab81d56fc45ec7dc76333383503b8abccfe
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@digia.com>