Diodon stopped run. I run it from the command line and got the error

Thanks for reporting. This is odd, it seems that in your clipboard history there is an item which is an empty string, which should not happen.

To check further, could you create a debug log file with the following commands and attach it:

killall diodon
G_MESSAGES_DEBUG=all diodon > diodon_debug.txt

Thanks.

https://pastebin.com/dgJCLXFJ

Looks all good. Strange. I assume most likely the error is in the database, which might be corrupt.

What you can do to test this is the following:

killall diodon
killall zeitgeist-daemon
mv ~/.local/share/zeitgeist/activity.sqlite ~/.local/share/zeitgeist/activity.sqlite.backup

and then start diodon again to see whether it works.

Let me know how it goes. If it works, we know there is an error in our code which does not handle such erroneous data cases gracefully.

after
killall zeitgeist-daemon
it works.

There is empty folder ~/.local/share/zeitgeist.
Yesterday I removed it and tried to run diodon, it didn't work.
killall zeitgeist-daemon helped. It works.

Problem solved

OK great. In case this error occurs again, please let me know, so we can take a closer look.