BHV-699: When the second panel doesn't have any spottable component, the...

... left arrow key doesn't move panel index to the previous.

### Issue:
When the second panel doesn't have any spottable component, the left arrow key doesn't move panel index to the previous.
### Fix:
In the updateSpotability method in moon.Panel, when not offscreen or in breadcrumb mode, check that the panel is Spottable. If not, create a dummy element.

Enyo-DCO-1.1-Signed-off-by: Krishna Rangarajan <krishna.rangarajan@lge.com>