How to ace_performSelectionChange in plugin within aceKeyEvent hook

[alexfrench]

I am trying to replace the selected text with some newText - always the same number of characters. When I do this using ace_replaceRange, the selection is lost and I would like to reset it. The ace_performSelectionChange function appears to be the way to do this, however, when I call it I get an error "cannot set properties of null (setting 'repChanged'). What am I doing wrong? Code excerpt below. Thanks so much.

exports.aceKeyEvent = (hookName, call) => {
...
editorInfo.ace_replaceRange (selStart, selEnd, newText);
editorInfo.ace_performSelectionChange(selStart, selEnd, false); // reset the selection
}