Thread:Project:Support desk/User Preferences don't offer Gadgets/reply (4)

In the meantime, I checked some options. (The MW configuration script tells that options aren't necessary, but they are very useful.) Nevertheless, nothing helps.

contains the line above, and this line only. I reduced the definition site to a simple gadget for testing.

The error log tells this:
 * (20024)The given path is misformatted or contained invalid characters: Cannot map GET /wiki/index.php/MediaWiki:Gadgets HTTP/1.1 to file, referer: http://localhost/wiki/index.php/MediaWiki:Gadgets-definition

Moreover, I found differences in : There must be a reason for the differences between WMF and MW. I suppose the same reason would lead to my problem's solution.
 * Generally (like in my local wiki), there are 8 tabs: beginning with User profile and ending with Misc
 * WMF projects add: Pending changes, Gadgets
 * MediaWiki adds: Edit review, Gadgets, Threaded discussion, Contests