audio player was initialized as having audio out by default, even if no audio output had beed created. This caused to always try to decode audio even when not required (like during commflagging)

Also, exit early in AVFD::ProcessAudioPacket if no one is listening.

Fixes #11616
Similar to c9d8533fe8fc19fead0ad896f37bb8f07367cc57, no need to attempt to decode audio if it's not going to be played