code: @Override
     public InputStream lookupFile(String filename, ClassLoader cl) {
        try {
           return lookupFileStrict( filename, cl );
        }
        catch (FileNotFoundException e) {
           return null;
        }
     }
docs: Looks up the file, see : {@link DefaultFileLookup}.
  
  @param filename might be the name of the file (too look it up in the class path) or an url to a file.
  @return an input stream to the file or null if nothing found through all lookup steps.