| (or) in combination with capturing parentheses doesn't work

[jens-duttke]

I have a problem with the | operator and capturing groups in my regexp:

const MultiRegExp2 = require('multi-regexp2').default;

const matches = new MultiRegExp2(new RegExp('(a)|(b)')).execForAllGroups('b', true);

console.log(matches);
// -> null

Normally the matches should looks like this:
https://regex101.com/r/jn9DU9/1

Full match	0-1	b
Group 2.	0-1	b