I posted this question previously but did not tag it properly (and hence why I likely did not get an answer) so I thought I would give it another shot as I haven't been able to find the answer in the meantime.
The below script is giving me the message in the title. I have another function which is using the same getValue method but it is running fine. What can I change in my script to avoid this issue?
function trashOldFiles() {
var ffile = SpreadsheetApp.getActiveSpreadsheet().getSheetByName("CtrlSht").getRange("B3:B3").getValue();
var files = DriveApp.getFilesByName(ffile);
while (files.hasNext()) {
var file = files.next();
var latestfile = DriveApp.getFileById(listLatestFile());
if(file.getId() ==! latestfile){
file.setTrashed(true);
}
}
};