sthal: fix vts test failure

note: The vts will use empty uuid to inject
      testing to hal.
      iaxxx hal doesn't consider the empty as exception
      case, that cause the cts failure.

Bug: 157862165
Test: run vts -m VtsHalSoundtriggerV2_0TargetTest locally
=============== Summary ===============
Total Run time: 32s
2/2 modules completed
Total Tests       : 12
PASSED            : 12
FAILED            : 0
============== End of Results ==============

Change-Id: I6e696ca8e1f4a5cafdc920a6da5b37193557dab6
1 file changed