…which was mentioned above
But thanks for filing a bug report - in fact, the usually suggested exercise of finding existing bugs before filing an own one is, IMO, a waste of time, and my usual advise is: you see something that, in your opinion, misbehaves - you don’t hesitate, and just file a new bug. For one, you could be intimidated by the huge bug database with hundreds of thousands of issues, where people use all kinds of language to express their problems, and get lost much easier than the triagers who know the usual issues well, and who can find duplicates much easier than you, and in the process of looking for a duplicate, an inexperienced user could loose their incentive to file it - and having a duplicate is so much better than not having it filed at all; and also, duplicates (and CCed people) have own value of indicating the importance and spread of the problem (we use these numbers as a metric of bug importance / severity, even more useful than the bugs’ respective meta fields).
The only pre-requisite to filing bugs must be the proper expectations, where the user does not take closing their bugs as not a bug as a personal insult: closing bugs in such a way is also a positive thing, where the user gets an explanation / reason for the behavior; and filing these (not-a-)bugs is also appreciated as an important contribution.