Audio Policy: Do not stop getOutputForAttr on invalid Mix

This would allow an app that successfully registered an invalid mix to
block all following mixes.

Test: none
Bug: 111453086
Change-Id: I3c1630b7b697dd70e08a5708d1515e097d683401
Signed-off-by: Kevin Rocard <krocard@google.com>
1 file changed