title: moodle file.php returns a blank 0 bytes file
body: <p>For some reason one installation of Moodle 1.9.3+  has a problem that file.php returns a blank 0 byte file sometimes, even the apache log shows 0 bytes were returned.   Another moodle installation works OK with the same htm files.</p>
  
  <p>What could be causing this? Problematic files are just usual htm files - bug occurs with links like this:</p>
  
  <p><a href="http://server/file.php/164/moddata/scorm/4/data/msg.htm" rel="nofollow noreferrer">http://server/file.php/164/moddata/scorm/4/data/msg.htm</a> </p>
  
  <p>(The problematic moodle was upgraded from 1.8 version earlier)</p>