Trying to access array offset on value of type null

On three unrelated sites we’re starting to see Trying to access array offset on value of type null from Mustache. If you look at checkIfTokenIsAllowedInParent in
Mustache/Parser.php around line 276 you’ll see that the signature allows $parent to be either an array or null, however the code itself doesn’t check for null.

This was fixed in Mustache with this commit, and it fixes our issues on all sites so far:
https://github.com/bobthecow/mustache.php/commit/6d28b0b28d941ac766092b13f65e56d63b782154

I’d be glad to send a PR for this however I’m not sure how you want to handle third-party code