CameraSettings: Do not crash if zoom ratios are not exposed

* On some devices, wrappers do not expose the zoom ratios, so the
  list of zoomRatios is empty. So the .add() method cant run from a
  null class. If zoom ratios are not exposed, simply return an empty
  list and the camera will take the default HAL's zoom ratios

-This fixes front camera photo shoot on jfltexx
Change-Id: Ic64e41a8c5a2d51966ec95d4b020e5d3951eac0e
1 file changed