I was able to fix this and would like to suggest a fix for the next update. Error handling could be useful here as well, so that ace.assets_url is only used when not empty, otherwise it should fall back to assets_url.
In assets/components/ace/modx.texteditor.js I changed:
In line 238:
In line 305:
In line 859:
In assets/components/ace/modx.texteditor.js I changed:
In line 238:
//var acePath = MODx.config['assets_url'] + 'components/ace/ace'; // old one var acePath = MODx.config['ace.assets_url'] + 'ace'; // new one
In line 305:
// net.loadScript(MODx.config['assets_url'] + 'emmet/emmet.js', function() { // old one net.loadScript(MODx.config['ace.assets_url'] + 'emmet/emmet.js', function() { // new one
In line 859:
// url: MODx.config['assets_url'] + 'completions.php', // old one url: MODx.config['ace.assets_url'] + 'completions.php', // new one