MediaScanner: Fix UnsupportedOperationException when scanning internal media

The media scanner was crashing while tring to insert genre data in the internal
media database, which does not support genres.
This resulted in some or all of the built in ringtones being unavailable

Bug: 5124718

Change-Id: Ib306348dd9808e59477b327b4adcb413957d8d24
Signed-off-by: Mike Lockwood <lockwood@android.com>