Issue: [4.1 Preview] "PHP: Unexpected error occurred. Please try again later" when liking wiki pages

Liking a wiki page throws an error: "Oops! We ran into some problems. Please try again later. More error details may be in the browser console."

The console message is "PHP: An unexpected error occurred. Please try again later."

Despite the error, the like is recorded just fine, and on a page reload I can see that the Like phrase has changed from 'Like' to 'Unlike'. Opening the '&do=like' link in a new tab also results in the same unexpected error message.

A more detailed error may be available if XF debug mode is enabled (or look at server errors in admin cp).