Mentat

When searching events, for example "not_categories=True" parameter can be added to the query parameters of the search, and the system then searches for all the categories except the chosen one. There are many more possible "not" queries in the event search.
But after the user clicks on the "search" button, the parameter disappears from the URL query parameters, which results in a completely different search. I found this problem because "not_category=True" is used in searching for report-related events, which makes this problem a bit more imporant than it seems at first.