0193be7c9b
(#17971) Although, pre- and post-linking functions are correctly called during directive linking, directives with `link.post` would throw an error. Interestingly, having `link.pre` only or defining `link: fn` (which is an alias for `link.post: fn`) would not throw. This commit removes this check and allows directives with pre- and/or post-linking functions to work.