Return null to signal no support for listFilesQuery() (#414)

Author: labkey-jeckels

panoramapublic/src/org/labkey/panoramapublic/PanoramaPublicFileListener.java

@@ -60,6 +60,6 @@ public Collection<File> listFiles(@Nullable Container container)
     @Override
     public SQLFragment listFilesQuery()
     {
-        throw new UnsupportedOperationException("Not implemented");
+        return null;
     }
 }