This is the actual device of the I2S or SPDIF controller reporting the
problem. If a future change converts these controllers to be CODECs, then
there may be no pcm associated with the substream, so this change avoids
a crash.
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>