Interesting. I wonder if there is a dodgy favicon somewhere in your database. Quite how it got in there is one question - it would be good if we can work it out and stop it happening again. Might be tough to work that out though, at least with the current version of KeePassRPC and Kee.
I’ll take a look at the KeePassRPC plugin in the next couple of days in case there is a way that we can ignore faulty icons rather than crash in the way that happens for you. Perhaps I’ll also be able to add some way of logging which entry triggers the crash.
You might be able to narrow down which entry(s) cause the problem by changing the Kee Home group in your database. First, take a backup copy of your kdbx file to make undoing this experiment easier and give us a test database that you can later use to test against the hypothetical future version of KeePassRPC I mention above. Then create a new empty group and one new entry inside it with just the default standard icon. Right click on the group and click the option to make that the Kee home group.
Now when you open that database and KeePassRPC sends the list of entries to Kee it will have just that one entry in it.
If that works, you could change the home group to different database groups and/or move entries around until you find which ones cause the problem.
If the problem still occurs with a single new entry, that doesn’t necessarily disprove the icon theory but it’ll make it tough to find out what’s happening using the current version of KeePassRPC.
Please let me know either way what you discover.