ALSA: jack: Check the return value of kstrdup()

kstrdup() can return NULL, it is better to check the return value of it.

Signed-off-by: Xiaoke Wang <xkernel.wang@foxmail.com>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/tencent_094816F3522E0DC704056C789352EBBF0606@qq.com


Signed-off-by: Takashi Iwai <tiwai@suse.de>