zephyr: Avoid crash on gc collect if zephyr_device_find() fails.

Signed-off-by: Daniel Campora <[email protected]>

Author: danicampora

ports/zephyr/machine_uart.c

@@ -163,8 +163,9 @@ static void mp_machine_uart_init_helper(machine_uart_obj_t *self, size_t n_args,
 static mp_obj_t mp_machine_uart_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *args) {
     mp_arg_check_num(n_args, n_kw, 1, MP_OBJ_FUN_ARGS_MAX, true);
 
+    const struct device *dev = zephyr_device_find(args[0]);
     machine_uart_obj_t *self = mp_obj_malloc_with_finaliser(machine_uart_obj_t, &machine_uart_type);
-    self->dev = zephyr_device_find(args[0]);
+    self->dev = dev;
     self->tx_complete = true;
 
     mp_map_t kw_args;