Invalid regular expression

[Agrumas]

Hi all,
there is issue with older mobile browsers on Android 8 or less.

Invalid regular expression: /[\p{Z}\p{S}\p{P}\p{C}]+/: Invalid escape

This regex that causes:

flexsearch/src/lang.js

Line 50 in 1243fd8

export const regex_whitespace = /[\p{Z}\p{S}\p{P}\p{C}]+/u;

It was reported a while back:
#296