stringprep room jids when we want to join a room

src/dialogs.py

@@ -786,6 +786,12 @@ _('You can not join a group chat unless you are connected.')).get_response()
 		server = self.xml.get_widget('server_entry').get_text().decode('utf-8')
 		password = self.xml.get_widget('password_entry').get_text().decode('utf-8')
 		jid = '%s@%s' % (room, server)
+		try:
+			jid = helpers.parse_jid(jid)
+		except:
+			ErrorDialog(_('Invalid room or server name'),
+		_('The room name or server name has not allowed characters.')
+			
 		if jid in self.recently_groupchat:
 			self.recently_groupchat.remove(jid)
 		self.recently_groupchat.insert(0, jid)