aft: Avoid implicit fallthrough in switch statement.

aft: Avoid implicit fallthrough in switch statement.

The missing return statement causes gcc-7 to complain:

	aft.c:2579:3: warning: this statement may fall through [-Wimplicit-fallthrough=]

And indeed, this fall through was not intended when the code in
question was introduced some months ago in commit a7a8d30e (Update
status items on blob events).

The issue is benign though, because also after falling through we
return 0.