See Category:Top level, as example. With trying clicking to [+] button near any subcategories, returned error message "categorytree-collapse-bullet: Parse error at position 0 in input: "
Topic on Project:Village Pump
I think this is bug 44459.
See Category:Top level, as example. With trying clicking to [+] button near any subcategories, returned error message "categorytree-collapse-bullet: Parse error at position 0 in input: "