Returns with an error notice if CHANNEL function of SIP channel is read without arguments.

(Closes issue #18653)
Reported by: wuwu
Patches:
      diff.patch uploaded by jrose (license 1225)
Tested by: jrose



git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.8@310088 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/sip/dialplan_functions.c

@@ -47,6 +47,13 @@ int sip_acf_channel_read(struct ast_channel *chan, const char *funcname, char *p
 		AST_APP_ARG(type);
 		AST_APP_ARG(field);
 	);
+		
+	/* Check for zero arguments */
+	if (ast_strlen_zero(parse)) {
+		ast_log(LOG_ERROR, "Cannot call %s without arguments\n", funcname);
+		return -1;
+	}
+
 	AST_STANDARD_APP_ARGS(args, parse);
 
 	/* Sanity check */