[syslog-ng] segfaults when a filter does not exist

I have recently produced a segfault in code version 1.6.9 when I use a filter which is not defined. In the example configuration snippet below, I left the filter 'f_test' undefined. Under normal conditions you will be unaware the process fails because it is backgrounded. If started with the '-F' argument, it reports a segfault on the command line. filter f_syslog { not facility(auth, authpriv) and not filter(f_test); };