Improve "one-way" error dialogs
Currently there are several actions in Fractal, namely starting a new private chat, entering a room or several others, that show (often too generic) error dialogs asynchronously, often some time after the action has been performed and not letting any kind of "recovery" (let's say correcting the room name, for example if # or the :server part is forgotten), giving often confusing feedback.
Meanwhile, dialogs like the "start direct chat" one seem to work properly, preventing users from creating a chat with non-existing users and allowing "recovery" in this way instead of just aborting and returning to the main view
Edited by Raffaele