I am not sure that this is how one closes a patch ^ , but that's the closest option I found..

And now about the other apps, I found out that actually there are quite a lot of apps that have this issue, not only the kcalc and the konsole.
So, there is no better option than just making one patch per app and submitting it on the phabricator, right?

Yep, I tested it before submitting a patch, and the warning is gone when I launch my compiled version of kcalc..
https://i.imgur.com/qSATbjg.png

I'm afraid that I'll need a bit of help in order to do that, sorry :-(
Git tells me that my copy is up-to-date, so I think that my patch is applied on top of most recent commit.
What exactly should I do to rebase it?

If this fix is correct, the same things should be probably done in some other apps, so far I found konsole to produce the same warning.

What about something like this?

Oh, and you are right again.
The previous solution seems to fix it without a regression, but obviously the code itself feels at the very least "not good".

Updated!
I didn't think about this solution, thanks, clearly it's way better than mine.

Ping

Yep, that's exactly what I did to fix that the first time I tried to write a patch!
The problem is, it doesn't solve it.
It will show the name of a folder wrong, if its url in places contains trailing slash (and it's easy to do, the patch that you linked still allows users to manually create/edit such urls in "places").
(The version which just always strips the trailing slash: https://i.imgur.com/QR0GGnx.png)

As far as I understand, nope, that commit just changes the url which is going to be added to "places".
Firstly, it doesn't fix the bug, and secondly, a user still can add/modify a url in places so that it contains a trailing slash, and current version of dolphin will show it's name wrong (if opened manually, as on the screenshots in "Test Plan").

Done

If this is not a desired default behavior, I'll need some hints on how to make a setting for it.

Thanks,