Fix a bug where Settings would crash from search into storage.

If the user entered the StorageDashboardFragment from search,
it would crash due to a precondition check added to the Storage
Manager. Because no volume id was set in the bundle for it to
check, it hits an assert that the volume id is not null causing
Settings to crash.

This sets a sensible default instead of null.

Bug: 34633464
Test: Manual. Entering through search does not crash now.
Change-Id: Ia6cd82929a0813eefcdad279436b9c2fe30b0146