[mod] lower indentantion, add a error message when not connected to a jabber server

jabber.py

@@ -1787,7 +1787,10 @@ def jabber_cmd_room(data, buffer, args):
     context = jabber_search_context(buffer)
     server = context["server"]
 
-    if server:
+    if not server:
+        weechat.prnt("", "Error: this command needs to be runned in a jabber server buffer, switch to a jabber buffer or use /jabber add|connect for that.")
+        return weechat.WEECHAT_RC_ERROR
+
     buddy = server.search_buddy_list(args, by='alias')
 
     if not buddy: