dm: core: Check for empty list in uclass_find_device()

This function needs to check the list has entries before traversing it.
Fix this bug.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

drivers/core/uclass.c

@@ -153,6 +153,8 @@ int uclass_find_device(enum uclass_id id, int index, struct udevice **devp)
 	ret = uclass_get(id, &uc);
 	if (ret)
 		return ret;
+	if (list_empty(&uc->dev_head))
+		return -ENODEV;
 
 	list_for_each_entry(dev, &uc->dev_head, uclass_node) {
 		if (!index--) {