Fix missing endcut errors propagating through links with title substitution

[iglunchadze]

When one file, say wo-endcut.md, has a {% cut "..." %} without an {% endcut %}, and another file, say index.md, has a link to it with title substitution ([{#T}](...)), the endcut error shows up not only for the first file, but for both:

ERR Cut must be closed in /index.md
ERR Cut must be closed in /wo-endcut.md

See the gist for examples of this and #9.

The endcut error should only show up for the file with the cut.