Fix problems with the Horde::errorHandler() call.
I currently get a fatal error whithin dynamic Imp (WSOD). Apparently
Horde::errorHandler() gets called during shutdown. The stack trace I
get from the error that Horde::errorHandler() tries to log looks like
this:
Stack trace:
#0 [internal function]: Horde::errorHandler('<!DOCTYPE html ...', 5)
#1 [internal function]: ob_gzhandler()
#2 {main}
While I still need to identify the source of this error I believe the
logMessage() method should always ensure it can actually log
something.