Catch IllegalStateException when updating Bluetooth A2DP codec info

Add an explicit check when calling getResources() inside
updateBluetoothA2dpConfigurationValues().
This fixes a potential race condition - the latter could be called
in background when processing intent update.

Bug: 35021206
Test: Manual UI testing
Change-Id: I38117c5b1e08f4b2ecfd7637bb3e34920aa0d296