Index: asterisk/channels/chan_sip.c
===================================================================
RCS file: /usr/cvsroot/asterisk/channels/chan_sip.c,v
retrieving revision 1.784
diff -u -r1.784 chan_sip.c
--- asterisk/channels/chan_sip.c	20 Jul 2005 17:05:18 -0000	1.784
+++ asterisk/channels/chan_sip.c	23 Jul 2005 04:05:53 -0000
@@ -2712,16 +2712,28 @@
 	static struct ast_frame null_frame = { AST_FRAME_NULL, };
 	switch(ast->fdno) {
 	case 0:
-		f = ast_rtp_read(p->rtp);	/* RTP Audio */
+		if (p->rtp)
+			f = ast_rtp_read(p->rtp);	/* RTP Audio */
+		else
+			f = &null_frame;
 		break;
 	case 1:
-		f = ast_rtcp_read(p->rtp);	/* RTCP Control Channel */
+		if (p->rtp)
+			f = ast_rtcp_read(p->rtp);	/* RTCP Control Channel */
+		else
+			f = &null_frame;
 		break;
 	case 2:
-		f = ast_rtp_read(p->vrtp);	/* RTP Video */
+		if (p->vrtp)
+			f = ast_rtp_read(p->vrtp);	/* RTP Video */
+		else
+			f = &null_frame;
 		break;
 	case 3:
-		f = ast_rtcp_read(p->vrtp);	/* RTCP Control Channel for video */
+		if (p->vrtp)
+			f = ast_rtcp_read(p->vrtp);	/* RTCP Control Channel for video */
+		else
+			f = &null_frame;
 		break;
 	default:
 		f = &null_frame;