I am running in to the following problem when trying to add new pages in the Sitemap in the Dashboard. Getting the following error message:

{"error":{"type":"Whoops\\Exception\\ErrorException","message":"Call to a member function getPageTemplateID() on a non-object","file":"\/opt\/lampp\/htdocs\/eset\/concrete\/src\/Page\/Type\/Type.php","line":292,"trace":[{"file":"\/opt\/lampp\/htdocs\/eset\/concrete\/src\/Page\/Type\/Type.php","line":292,"function":null,"class":null,"args":[]}]},"errors":["Call to a member function getPageTemplateID() on a non-object"]}

I am running C5.7.4.2 incrementally updated from C5.7.3. The error message popup appears twice and it doesn't matter which page template I choose.

I can still change page templates in the Design & Type options in the sitemap and the page design options on a particular page.

Any help is appreciated.