Bug 2152958

Description of problem:
I had set up phone filesystem access in the past.
It no longer works, I'm getting "Chyba při přístupu k souborovému systému. sshfs byl ukončen s kódem 1" (= Error accessing filesystem. Sshfs exited with code 1.)

Version-Release number of selected component (if applicable):
kde-connect-22.08.3-1.fc37.x86_64

How reproducible:
always

Steps to Reproduce:
1. install kdeconnect on the computer and the phone, pair them
2. in kdeconnect on phone, go to modules settings
3. enable filesystem access module, add a share
4. on the computer, open dolphin
5. try to open your phone from the devices list
6. try to access the share

Actual results:
5. there is a lock icon over the share icon and computer is flooded with errors "Chyba při přístupu k souborovému systému. sshfs byl ukončen s kódem 1"
(Error accessing filesystem. Sshfs exited with code 1.)

6. Soubor nebo složka /run/user/1000/fb712b4e8a4627e9/primary neexistuje.
(File or folder ... does not exist.)

Expected results:
5. no lock over the share icon, no errors
6. you can open the share and see the files and folders on your phone

Additional info:
note that checking apps permissions on the phone, I have found that kdeconnect does not have the filesystem access privilege, which looks like a nonsense as it has worked in the past - I've enabled it but it still does not work

trying to add a new share, I got a question whether I would like to enable kdeconnect to access the folder ... why, if it already has the filesystem access? and even if I answer yes, I am asked again when retrying to add the same folder

- note that I don't see any method to remove the share, only to uncheck it


and also note, even if this turns out to be problem in the mobile part, there are still two things to be fixed in the desktop part:
1) if there's an error, don't flood the desktop with the error message announcements, one is enough
2) print some sane error message which indicates what the problem is

from journal:

pro 13 16:14:21 kvolny kdeconnectd[173465]: /usr/bin/fusermount: entry for /run/user/1000/fb712b4e8a4627e9 not found in /etc/mtab
pro 13 16:14:21 kvolny kdeconnectd[1961]: QDBusAbstractAdaptor: Cannot relay signal SftpPlugin::packetReceived(NetworkPacket): Unregistered input type in parameter list: NetworkPacket