Merge "MuxerTest:Added tests for allowing empty tracks" into rvc-qpr-dev am: 63aa64398f am: 3e6efdd34f

Original change: https://googleplex-android-review.googlesource.com/c/platform/cts/+/12700374

Change-Id: I4914ff491488b31161b1c2374f30dc2f738aca3a