This issue affects me too.
I have several blacklist and whitelist entries. I have been managing these via the web interface for months.
I have just upgraded my pihole to the latest version. After doing this the list of whitelist and blacklist entries on their respective management pages are now completely empty.
The activated blacklist items continue to block the content, but I cannot switch them on or off because the lists on the management pages are empty.
Any help would be appreciated.