Fix compilation warning.

diff --git a/tools/testing/selftests/net/psock_tpacket.c b/tools/testing/selftests/net/psock_tpacket.c
index 8cb5127c42af..e795a41c4771 100644
--- a/tools/testing/selftests/net/psock_tpacket.c
+++ b/tools/testing/selftests/net/psock_tpacket.c
@@ -377,6 +377,7 @@ static inline void *get_next_frame(struct ring *ring, int n)
 		return f0 + (n * ring->req3.tp_frame_size);
 	default:
 		bug_on(1);
+		return NULL;
 	}
 }