Firewall log is empty in the GUI
On SG-3100 (and likely others), the GUI firewall log is empty. The contents of /var/log/filter.log appear correct, but no entries are parsed and shown in the GUI. Additionally, filterparser.php produces no output. Thus it's likely a problem parsing the log and not a problem with the GUI page.
Might have some relation to #9411, but still happens on systems that appear to have valid/properly formatted log files.