Add missing return in GetMediaPlayerListResponse

There was a missing return in GetMediaPlayerListResponse resulting in
two messages sent if no player was available (one with error code,
the other with no error and empty players list).
We should only return RANGE_OUT_OF_BOUNDS when it's the case.

Bug: 328847183
Flag: exempt trivial
Test: atest BluetoothInstrumentationTests
Change-Id: I26637d4a310ba3b06c21d9d1d1f210351abd4f81