uterm_input: fix increasing refcnt

We need to correctly increase the refcnt. We currently increase it only
when it was 0 before due to a very subtle bug as we missed the "return".

Signed-off-by: David Herrmann <dh.herrmann@googlemail.com>

src/uterm_input.c

@@ -275,6 +275,7 @@ err_free:
 void uterm_input_ref(struct uterm_input *input)
 {
 	if (!input || !input->ref)
+		return;
 
 	++input->ref;
 }