coverity: sdp_msg_test.c: check rc of sdp_msg_from_sdp_str()

Related: CID#310975
Change-Id: I69d8972c58fb7cde965ff0b231947dd26247c2c7
diff --git a/tests/sdp_msg/sdp_msg_test.c b/tests/sdp_msg/sdp_msg_test.c
index a1ffac0..ebe8328 100644
--- a/tests/sdp_msg/sdp_msg_test.c
+++ b/tests/sdp_msg/sdp_msg_test.c
@@ -136,7 +136,7 @@
 		printf("\n[%d]\n", i);
 		dump_sdp(t->sdp_input, "sdp input: ");
 
-		sdp_msg_from_sdp_str(&sdp, t->sdp_input);
+		OSMO_ASSERT(sdp_msg_from_sdp_str(&sdp, t->sdp_input) == 0);
 		sdp_msg_to_sdp_str_buf(str, sizeof(str), &sdp);
 
 		dump_sdp(str, "sdp_msg_to_sdp_str_buf: ");