Zip service crashes

The zip service often crashes on its own. I think the condition is that there are no temporary files to delete, or maybe the directory for temporary files does not exist?
```
Running on port 3011
/home/node/app/dist/app.js:48
files.forEach(function (file) {
^
TypeError: Cannot read property 'forEach' of undefined
at /home/node/app/dist/app.js:48:19 
```