Error detected while processing BufEnter Autocommands for "*": E495: No autocommand file name to substitute for "<afile>"

[cewood]

Describe the bug:

Since version v4.9.10 (2716792) vim-polyglot itself generates the following error during startup.

Error detected while processing BufEnter Autocommands for "*":
E495: No autocommand file name to substitute for "<afile>"

I believe the issue is with vim-polyglot itself, by way of the error messages reported, as well as the diff of changes between the last working version (v4.9.9), and the first problematic version (v4.9.10).

v4.9.9...v4.9.10

To Reproduce:

Install any version from v4.9.10 upwards (Sep 15, 2020), and the error will be reported during startup.

The following is an extended version of the error from a debug log.

Executing BufEnter Autocommands for "*"
autocommand if &ft == "" && expand("<afile>") !~ g:ft_ignore_pat | call s:observe_filetype() | endif

Error detected while processing BufEnter Autocommands for "*":
E495: No autocommand file name to substitute for "<afile>"
Executing BufEnter Autocommands for "*"
autocommand lua require("trouble").action("on_win_enter")