misternikitas It seems like the database file to store your game data has been corrupted. Could you navigate to "...\Documents\LoLReplay2" and send me the "games_new.db" file to email@example.com? This should help me in figuring out how that came to be.
As for a fix, after sending that file over you can rename it, and restart the tool. You'll have to use the "Load missing games" feature afterwards to re-add the data to the database.