Bluetooth: host: missing NULL check in bt_le_create_conn_cancel

[JordanYates]

Describe the bug

Due to a missing NULL check in bt_le_create_conn_cancel a NULL pointer can be provided to bt_hci_cmd_state_set_init, causing a fault.

zephyr/subsys/bluetooth/host/hci_core.c

Lines 860 to 862 in b6c8212

	buf = bt_hci_cmd_create(BT_HCI_OP_LE_CREATE_CONN_CANCEL, 0);
	bt_hci_cmd_state_set_init(buf, &state, bt_dev.flags,

Expected behavior

Return value of bt_hci_cmd_create should be checked before use.

Impact

Program faults

Environment (please complete the following information):

• Zephyr v3.7.0
• Zephyr v4.0.0