samd: audio_dma_stop: don't free invalid channel

audio_dma_stop can be reached twice in normal usage of AudioOut.

This may bear further investigation, but stop it here, by making the
function check for a previously freed channel number.  This also prevents
the event channel from being disabled twice.

The first stop location is from audio_dma_get_playing, when the buffers
are exhausted; the second is from common_hal_audioio_audioout_stop when
checking the 'playing' flag.

0 files changed, 0 insertions, 0 deletions