same error to my installations. I upgraded two sites from 1.0.15 to 1.2.1, first on my localhost (xampp - three year old installation!) and everything was fine. After uploading sites and Databases to my webhost, i can't enter the config tab. If i click the config-tab, i'm getting an 500 Error!
Running an Apache with PHP 7.1 and MySQL
Strange thing in this context: If i click the button before the config tab to "export site" i'm getting an js-error in tabpane.js:
Uncaught TypeError: Cannot read property 'length' of undefined
at WebFXTabPane.addTabPage (tabpane.js:126)
WebFXTabPane.addTabPage @ tabpane.js:126
(anonymous) @ index.php?a=83:187
But it's confusing me, that the local installation is runnung perfect on my old environment and not on my webserver - any ideas for me?