Notice: Undefined variable: page_form

[N4zroth]

Hey,
as far as I can remember, I changed nothing ( ), but suddenly the message

Notice: Undefined variable: page_form in /usr/local/ispconfig/interface/web/sites/web_domain_edit.php on line 497 Notice: Trying to get property of non-object in /usr/local/ispconfig/interface/web/sites/web_domain_edit.php on line 497 Notice: Undefined variable: page_form in /usr/local/ispconfig/interface/web/sites/web_domain_edit.php on line 498 Notice: Trying to get property of non-object in /usr/local/ispconfig/interface/web/sites/web_domain_edit.php on line 498 Notice: Undefined variable: page_form in /usr/local/ispconfig/interface/web/sites/web_domain_edit.php on line 499 Notice: Trying to get property of non-object in /usr/local/ispconfig/interface/web/sites/web_domain_edit.php on line 499 Notice: Undefined variable: page_form in /usr/local/ispconfig/interface/web/sites/web_domain_edit.php on line 500 Notice: Trying to get property of non-object in /usr/local/ispconfig/interface/web/sites/web_domain_edit.php on line 500 Notice: Undefined index: on_after_update in /usr/local/ispconfig/interface/lib/classes/plugin.inc.php on line 140 Notice: Undefined index: sites:on_after_update in /usr/local/ispconfig/interface/lib/classes/plugin.inc.php on line 140 Notice: Undefined index: sites:web_domain:on_after_update in /usr/local/ispconfig/interface/lib/classes/plugin.inc.php on line 140 Notice: Undefined index: global in /usr/local/ispconfig/interface/lib/classes/getconf.inc.php on line 50

started appearing in the redirect tab, regardless of which site module was openend (Website/Subdomain/etc.).
ISPConfig seems to work fine, but what do I do to repair it and remove the error?
Thanks a lot.

Edit: It appears and refuses to go away, as soon as I click on any tab, regardless of which website module I'm in. Also, another error message appears in other modules, e. g. for editing FTP Users. But these errors appear only upon clicking on a tab. Any ideas?

[till]

You seem to have enabled developer notices in PHP. Edit the php.ini file on your server and change the error_reporting level to show only errors and not notices.

[N4zroth]

Hey,
sorry for not answering. Somehow, I didn't get notified that an answer to my question was posted. I'll try out what you said.
Thanks for your help