gtphub: check for gsn_addr_from_sockaddr() errors

Previously the return value was ignored. Check it and log error message.

Change-Id: If6babdad650dc6a84e6a784fc8d3c5abe146ecc1
diff --git a/src/gprs/gtphub.c b/src/gprs/gtphub.c
index b0e75ca..2ff1b7c 100644
--- a/src/gprs/gtphub.c
+++ b/src/gprs/gtphub.c
@@ -1583,7 +1583,9 @@
 		 * gtphub_handle_buf(), we'd be creating a peer port just to
 		 * expire it right away. */
 		if (hub->sgsn_use_sender && (side_idx == GTPH_SIDE_SGSN)) {
-			gsn_addr_from_sockaddr(&use_addr, &use_port, &from_ctrl->sa);
+			int rc = gsn_addr_from_sockaddr(&use_addr, &use_port, &from_ctrl->sa);
+			if (rc < 0)
+				LOG(LOGL_ERROR, "%s(): failed to obtain GSN address\n", __func__);
 		} else {
 			use_port = gtphub_plane_idx_default_port[plane_idx];
 
@@ -2765,7 +2767,9 @@
 
 	struct gsn_addr gsna;
 	uint16_t port;
-	gsn_addr_from_sockaddr(&gsna, &port, addr);
+	int rc = gsn_addr_from_sockaddr(&gsna, &port, addr);
+	if (rc < 0)
+		LOG(LOGL_ERROR, "%s(): failed to obtain GSN address\n", __func__);
 
 	pa = gtphub_addr_find(bind, &gsna);
 	if (!pa)