res_rtp_asterisk: Fix crash when RTCP is not present when DTLS is stopped.

This change removes an assumption that when DTLS is stopped
an RTCP session will be present on the RTP session. This is not
always the case.

ASTERISK-26732

Change-Id: Ib9f7c09ce0b005efe362dbcc8795202b18f94611

res/res_rtp_asterisk.c

@@ -1577,7 +1577,7 @@ static int ast_rtp_dtls_active(struct ast_rtp_instance *instance)
 static void ast_rtp_dtls_stop(struct ast_rtp_instance *instance)
 {
 	struct ast_rtp *rtp = ast_rtp_instance_get_data(instance);
-	int rtcp_dtls_unique = (rtp->dtls.ssl != rtp->rtcp->dtls.ssl);
+	SSL *ssl = rtp->dtls.ssl;
 
 	dtls_srtp_stop_timeout_timer(instance, rtp, 0);
 
@@ -1595,7 +1595,7 @@ static void ast_rtp_dtls_stop(struct ast_rtp_instance *instance)
 	if (rtp->rtcp) {
 		dtls_srtp_stop_timeout_timer(instance, rtp, 1);
 
-		if (rtp->rtcp->dtls.ssl && rtcp_dtls_unique) {
+		if (rtp->rtcp->dtls.ssl && (rtp->rtcp->dtls.ssl != ssl)) {
 			SSL_free(rtp->rtcp->dtls.ssl);
 			rtp->rtcp->dtls.ssl = NULL;
 			ast_mutex_destroy(&rtp->rtcp->dtls.lock);