hctl: Remove a useless assert
hctl: Remove a useless assert

The case where the element is unavailable (for example gone away since
the event was created) is handled beneath.

See also bug 5471.
	https://bugtrack.alsa-project.org/alsa-bug/view.php?id=5471

Signed-off-by: Takashi Iwai <4596b3305151c7ee743192a95d394341e3d3b644@suse.de>

tiwai/alsa-lib,alsa-project/alsa-lib,mengdonglin/alsa-lib,zedongchen/alsa-lib,zedongchen/alsa-lib,mikelima/alsa-lib,tiwai/alsa-lib,mikelima/alsa-lib,mengdonglin/alsa-lib,mengdonglin/alsa-lib,lgirdwood/alsa-lib,lgirdwood/alsa-lib,takaswie/alsa-lib,mikelima/alsa-lib,takaswie/alsa-lib,mengdonglin/alsa-lib,mengdonglin/alsa-lib,zedongchen/alsa-lib,alsa-project/alsa-lib,tiwai/alsa-lib,lgirdwood/alsa-lib,Distrotech/alsa-lib,takaswie/alsa-lib,Distrotech/alsa-lib,tiwai/alsa-lib,mikelima/alsa-lib,Distrotech/alsa-lib,zedongchen/alsa-lib,Distrotech/alsa-lib,lgirdwood/alsa-lib,zedongchen/alsa-lib,alsa-project/alsa-lib,takaswie/alsa-lib,alsa-project/alsa-lib,Distrotech/alsa-lib,takaswie/alsa-lib,mikelima/alsa-lib,lgirdwood/alsa-lib