Cache Manifest Node. Error in console (error event) offline?

Question

HTML

Good evening!
Set up an offline web application.
When online, the files get into the cache and this is written in the console (how to get rid of these lines in the console?)
We go offline, the application works, but an error is written to the console:

Application Cache Error event: Manifest fetch failed (6)

On node I catch /cache.mf (which is written in html)

app.get('/cache.mf', function(q, s) {
  s.header('content-type', 'text/cache-manifest');
  return s.end([
'CACHE MANIFEST', 
'CACHE:', 
'/', 'styles/preloader.css', 'styles/all.css', 'scripts/all.js', 'images/bg.png', 'fonts/icomoon.eot', 'fonts/icomoon.svg', 'fonts/icomoon.ttf', 'fonts/icomoon.woff', 
'NETWORK:', 
'*', 
'FALLBACK:', 
'images/store/ images/offline.jpg'].join('\n'));
});

The cache.mf file itself does not exist (I tried to create it, the result is the same).