Handle null DownloadManager

If the DownloadManager has been disabled by the user via Settings for
instance, DownloadManager can be null, so MediaProvider should handle
it gracefully

Test: Manual
Bug: 178679250
Merged-In: If7b94298f281a31ffb6b4f829161c5f5dc44317d
Change-Id: I313f1239d1551cdbff6a58e35769d3495eb043da
1 file changed