logging: Fix logging after introduction of the early check

The introduction of a 'if + do {} while' lead to not being able to
return the result of the logging anymore. Just return.
diff --git a/src/link_udp.c b/src/link_udp.c
index e1fabc6..85f6c09 100644
--- a/src/link_udp.c
+++ b/src/link_udp.c
@@ -305,8 +305,10 @@
 	struct mtp_link *link;
 
 	ulink = session->data;
-	if (!ulink)
-		return LOGP(DINP, LOGL_ERROR, "Failed to find link_id %d\n", link_id);
+	if (!ulink) {
+		LOGP(DINP, LOGL_ERROR, "Failed to find link_id %d\n", link_id);
+		return;
+	}
 
 	link = ulink->base;