FS-9135: handle null sdp sent to switch_core_media_set_sdp_codec_string

src/switch_core_media.c

@@ -10096,6 +10096,7 @@ SWITCH_DECLARE(void) switch_core_media_set_sdp_codec_string(switch_core_session_
 	}
 
 	if (!r_sdp) {
+		switch_log_printf(SWITCH_CHANNEL_SESSION_LOG(session), SWITCH_LOG_WARNING, "Setting NULL SDP is invalid\n");
 		return;
 	}