Make sure call is valid when handling mini-frame.

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@2754 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_iax2.c

@@ -4556,6 +4556,7 @@ static int socket_read(int *id, int fd, short events, void *cbdata)
 					   drop it, since we don't have a scallno to use for an INVAL */
 					/* Process as a mini frame */
 					f.frametype = AST_FRAME_VOICE;
+					if (iaxs[fr.callno]) {
 						if (iaxs[fr.callno]->voiceformat > 0) {
 							f.subclass = iaxs[fr.callno]->voiceformat;
 							f.datalen = len;
@@ -4594,6 +4595,7 @@ static int socket_read(int *id, int fd, short events, void *cbdata)
 							ast_log(LOG_WARNING, "Received trunked frame before first full voice frame\n ");
 							iax2_vnak(fr.callno);
 						}
+					}
 					ast_mutex_unlock(&iaxsl[fr.callno]);
 				}
 				ptr += len;