I am experiencing application crashes when accessing webdav as well.
But I don’t see the error message you are seeing. For it just says “Application Error - The application GUI just crashed”. My RC is on version 6.4.3
I also get a crash of the electron client for Linux with
Application Error
The application GUI just crashed.
I can define the Webdav server without errors, but when I try to access it, it starts building up a selection box and then crashes.
Enabling the dev tools beforehand does not give me any hint. Only some “invalid color” stacktrace, that surely can’t be the reason.
I’ve got the same behaviour and was testing against the official nextcloud demo server.
Server could be added in a channel, but when trying to use/access it, the GUI crashes.
RocketChat Version 6.4.1