tests: Missing return statement

Change-Id: I4fae9f84a83af280846b07eaa139ff4a05784a2e
diff --git a/src/tests/hnb-test.c b/src/tests/hnb-test.c
index 446a14a..27959ec 100644
--- a/src/tests/hnb-test.c
+++ b/src/tests/hnb-test.c
@@ -326,7 +326,7 @@
 
 	if (len < sizeof(*ar)) {
 		printf("GSM48 Auth Req does not fit.\n");
-		return;
+		return -1;
 	}
 
 	printf(" :) Authentication Request :)\n");