ASoC: SOF: sof-audio: prepare_widgets: Check swidget for NULL on sink failure

ASoC: SOF: sof-audio: prepare_widgets: Check swidget for NULL on sink failure

commit b2c2914e7fe73571127853fd2087ffe9e2b2584e upstream.

If the swidget is NULL we skip the preparing of the widget and jump to
handle the sink path of the widget.
If the prepare fails in this case we would undo the prepare but the swidget
is NULL (we skipped the prepare for the widget).

To avoid NULL pointer dereference in this case we must check swidget
against NULL pointer once again.

Fixes: 7e1ca5de0401 ("ASoC: SOF: sof-audio: skip prepare/unprepare if swidget is NULL")
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20230120102125.30653-1-peter.ujfalusi@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>