Bluetooth: Audio: Fix segmentation issue in BT Audio shell
Bluetooth: Audio: Fix segmentation issue in BT Audio shell

It was possible to enter a state where setting the QoS
for a source stream after having released a sink stream
as the unicast client would cause a segmentation error.
This issue is related to how the unicast shell is using
the unicast group.

A fix has been added for it, and a check for
whether or not `audio init` (to register the needed
callback) has been added. This check has also been added
for the broadcast sink.

Signed-off-by: Emil Gydesen <a20314356615223738233ab4c4eb1cd8cd4146fa@nordicsemi.no>

galak/zephyr,finikorg/zephyr,galak/zephyr,finikorg/zephyr,galak/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr