Describe the bug
The generated treeview and related page do not reflect page and subpage structure from markdown pages.
This happens when a subpage is referenced in one file, while the defined page is in another markdown file.

Expected behavior
The treeview and related pages should reflect page and subpage given in markdown pages.

Screenshots
In this example sub inner is defined in the same file as main page, while sub outer is defined in another file (see attached zip to reprodue).
doxygen 1.9.2 (correct)

doxygen 1.9.3 (buggy)

To Reproduce
test.zip

doxygen ./Doxyfile.193
only non std vars are

GENERATE_TREEVIEW      = YES 
INPUT                  = main.md main-sub-outer.md
FILE_PATTERNS          =

Version
Bug seen on 1.9.3 and master 1.9.4 (d7e47e1)
works with 1.9.2
build from github repo.

Distributor ID: Debian
Description: Debian GNU/Linux 11 (bullseye)
Release: 11
Codename: bullseye