BassClientServiceTest: Ignore intents when BassClientService is null

There is possibility that in test teardown an intent may come which will
be stored on device queue to parse in test. When there is no service,
this intent should be ignored.

Flag: Exempt, test only
Test: atest BassClientServiceTest
Bug: 332048275
Change-Id: Ica5fb93f7a5df52faab744c4b58399cfc7c35658