Bluetooth: shell: Fix null check in cmd_per_adv_sync_delete
Bluetooth: shell: Fix null check in cmd_per_adv_sync_delete

The check for NULL was on the pointer to the pointer,
rather than the pointer. The pointer of the pointer would
always be non-null, but the pointer might not be.

Moved from using a pointer of a pointer to just a
pointer to make it easier to read and understand.

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

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