Applescript `document` method not recognized

Steps to reproduce

1. Create an Applescript that opens MacVim and calls document 1. Eg:

tell application MacVim
    activate
    set my_path to get path of document 1
end tell

2. Execute script with osascript script_name.
3. Find the error: Can’t get document 1. Invalid index. (-1719)

See more details here.

Expected behaviour

get path of document 1 should return the file path of the first document being currently displayed. I believe it's also called the 'front document'.

Version of Vim and architecture

9.0.65 (173)

Environment

Operating System: Bug Sur version 11.6.8 (20G730)
Terminal: Using MacVim GUI, not a terminal. It's version shows the Vim version 9.0.65 (173). It also says c2007 Bjorn Winckler.
Value of $TERM: xterm-256color

How MacVim was installed

brew install macvim

Logs and stack traces

Don't find any log or other error besides what's displayed.  Maybe I don't know how to turn on verbose logging?

Vim configuration where issue is reproducable

No response

Issue has been tested with given configuration

• by running MacVim.app from GUI macOS interface
• by running vim/gvim/etc installed by MacVim
• by running other versions of vim (e.g. /usr/bin/vim)

Issue has been tested with no configuration

• by running mvim --clean (or gvim, supplied by MacVim distribution)
• by running vim --clean (in terminal, supplied by MacVim distribution)
• by running vim --clean (in terminal, other suppliers, e.g. /usr/bin/vim)

Other conditions

• The both Homebrew packages "vim" and "macvim" are installed

Keine Quelldatei oder kein Test ist angegeben. Beginne damit, den Fehler mit dem gezeigten AppleScript zu reproduzieren, und untersuche das AppleScript-Wörterbuch von MacVim und die Dokumentverarbeitung; als erledigt gilt, wenn get path of document 1 den Pfad des vordersten Dokuments ohne den Fehler wegen eines ungültigen Index zurückgibt.