title: Symfony2 - Attempting to view my site in prod environment results in a blank screen; no errors/warnings in dev
body: <p>Cross-posted from the official Symfony Google Group because time is an issue:</p>
  
  <p>I'm in the final push to upload my site to my host.  Everything runs fine in the dev environment - no errors, no warnings.  When I attempt to access it in prod (localhost/web/app.php/), I get a blank screen.  I attempted to clear the cache, to see if that would help, but got the following error:</p>
  
  <pre><code>$ app/console cache:clear --env=prod
  
  [Symfony\Component\DependencyInjection\Exception\InvalidArgumentException] 
  The parameter "kernel.trusted_proxies" must be defined. 
  </code></pre>
  
  <p>I can clear the dev cache without issue.</p>
  
  <p>Please help.</p>