Version 2.3.1 not working

I have just upgraded plugin to 2.3.1 to my local site that I am developing on my PC. However it fails each time (i.e. simply entered a search string such as the filename of an image I want to find) then click Search). Previous versions were OK.

Here is error report I got:

Plugin: 2.3.1
WordPress: 5.5.1 (single)
PHP: 7.3.17 512M 1200s
Browser: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:80.0) Gecko/20100101 Firefox/80.0
JavaScript: https://localhost/wordpress/wp-content/plugins/search-regex/search-regex.js
REST API: https://localhost/wordpress/wp-json/
Query: ?page=search-regex.php&searchphrase=fr-runners-graphic.jpg
Buster: 2.3.1 === 2.3.1

TypeError: e is undefined

in Unknown
in f
in Ul
in Unknown
in f
in Unknown
in f
in yc
in tu
in div
in u
in Unknown
in f
in StrictMode
in Le
in Oc