PHP warning in wp-includes/canonical.php when accessing custom feed with specific permalink structure

[mt8.biz]

Problem:
Path lookup fails within redirect_canonical() when accessing custom feeds for certain permalink structures.

Error Message:

<b>Warning</b>:  Undefined array key "path" in <b>/path/to/wordpress/wp-includes/canonical.php</b> on line <b>618</b><br />
<br />
<b>Warning</b>:  Undefined array key "path" in <b>/path/to/wordpress/wp-includes/ccanonical.php</b> on line <b>618</b><br />
<br />
<b>Warning</b>:  Undefined array key "path" in <b>/path/to/wordpress/wp-includes/ccanonical.php</b> on line <b>730</b><br />
<error>

Error location (6.6 branch):
​https://github.com/WordPress/wordpress-develop/blob/6.6/src/wp-includes/canonical.php#L617-L618
​https://github.com/WordPress/wordpress-develop/blob/6.6/src/wp-includes/canonical.php#L730

Reproduction steps:

• Install WordPress 6.6.1
• Set permalink structure to /%category%/%post_id%
• Access {WordPress URL}/?feed=test

*?feed=test is a non-existent feed template

Version confirmed this issue:
WordPress: 6.6.1
Theme: Twenty Twenty-Four
Plugin: None

https://core.trac.wordpress.org/ticket/62007