SwingJS 5.x won't compile jalview.util.StringUtils.DELIMITERS_PATTERN

JalviewJS 12.x can't be run because a previously working in SwingJS regex:
DELIMITERS_PATTERN = Pattern
          .compile(".*='[^']*(?!')");

Now throws a JS error:
FileLoader.js:315 Uncaught SyntaxError: Invalid regular expression: /(?<秘1>.*='[^']*)(?(?<秘2>!'))/g: Invalid group (at Pattern.js:183:8)
    at new RegExp (<anonymous>)
    at clazz.eval [as newRegExp$S$S] (Pattern.js:183:8)
    at clazz.eval (Pattern.js:147:16)
..

The problem looks to be due to a patch for https://github.com/BobHanson/java2script/issues/253 which inserts zero length markers at capture groups, which for our case results in an invalid regex:
".*='[^']*(?!')"

becomes
"(?<秘1>.*='[^']*)(?(?<秘2>!'))"

The problem is most likely that the groups patch doesn't allow for zero width negative lookahead - JS didn't support this widely until ~2022, so understandable that this syntax wasn't tested.