--- /root/univention-support/room_management.py.bak     2023-12-22 13:06:57.604699671 +0100                           
+++ /usr/lib/python3/dist-packages/univention/management/console/modules/computerroom/room_management.py        2023-1
2-22 13:32:29.610403419 +0100                                                                                         
@@ -94,11 +94,14 @@
 
     def validate_userstr(self, userstr):  # type: (str) -> str
         match = self._user_regex.match(userstr)
-        if not match or not userstr:
+        if not userstr:
             raise AttributeError("invalid key {!r}".format(userstr))
-        username = match.groupdict()["username"]
-        if not username:
-            raise AttributeError("username missing: {!r}".format(userstr))
+        if match:
+            username = match.groupdict()["username"]
+        else:
+            username = ""
+        #if not username:
+        #    raise AttributeError("username missing: {!r}".format(userstr))
         return username
 
     @LDAP_Connection()