fixes a bug "No expression before quantifier" with Saxon-PE 9.5.1.3

Funnily, this doesn’t arise with current eXist but eXist’s
dashboard/plugins/userManager/jsjson.xqm (which looks like a direct
clone of this file) removes these characters as well
Merge pull request #8 from peterstadler/master

fixes a bug "No expression before quantifier" with Saxon-PE 9.5.1.3