mgcp_sdp: fix potential leak

Change-Id: I31527b54f602634024a0b687eef26a9b29354282
diff --git a/src/libosmo-mgcp/mgcp_sdp.c b/src/libosmo-mgcp/mgcp_sdp.c
index 0759c96..eabaf53 100644
--- a/src/libosmo-mgcp/mgcp_sdp.c
+++ b/src/libosmo-mgcp/mgcp_sdp.c
@@ -394,8 +394,10 @@
 				codecs_used = rc;
 			break;
 		case 'c':
-			if (audio_ip_from_sdp(&rtp->addr, line) < 0)
+			if (audio_ip_from_sdp(&rtp->addr, line) < 0) {
+				talloc_free(tmp_ctx);
 				return -1;
+			}
 			break;
 		default:
 			if (endp)