Add checks when retrieving data for the JNI layer for AVRCP

Bug: 80510649
Test: Call getPlayStatus after the service has stopped and see that a
crash doesn't occur.

Change-Id: I1ce7618296d83d60ee78ede405e7334a43970047
Merged-In: I1ce7618296d83d60ee78ede405e7334a43970047
(cherry picked from commit 0687431c)