fix seg fault (bug #2772)

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/v1-0@4226 65c4cc65-6c06-0410-ace0-fbb531ad65f3

CHANGES

@@ -1,3 +1,5 @@
+ -- rtp
+    -- fix for a seg fault
  -- chan_sip
     -- fix to prevent seg fault when attempting a transfer
     -- fix bug with supervised transfers

rtp.c

@@ -472,14 +472,14 @@ struct ast_frame *ast_rtp_read(struct ast_rtp *rtp)
 	    if (rtp->lasteventseqn <= seqno) {
 	      f = process_rfc2833(rtp, rtp->rawdata + AST_FRIENDLY_OFFSET + hdrlen, res - hdrlen);
 	      rtp->lasteventseqn = seqno;
-	    }
+	    } else f = NULL;
 	    if (f) return f; else return &null_frame;
 	  } else if (rtpPT.code == AST_RTP_CISCO_DTMF) {
 	    /* It's really special -- process it the Cisco way */
 	    if (rtp->lasteventseqn <= seqno) {
 	      f = process_cisco_dtmf(rtp, rtp->rawdata + AST_FRIENDLY_OFFSET + hdrlen, res - hdrlen);
 	      rtp->lasteventseqn = seqno;
-	    }
+	    } else f = NULL;
 	    if (f) return f; else return &null_frame;
 	  } else if (rtpPT.code == AST_RTP_CN) {
 	    /* Comfort Noise */