Undo revert from merge

modules/exploits/multi/http/mediawiki_thumb.rb

@@ -170,7 +170,7 @@ class Metasploit3 < Msf::Exploit::Remote
 
     # If we have already identified a DjVu file on the server trigger
     # the exploit
-    if datastore['FILENAME']
+    unless datastore['FILENAME'].blank?
       payload_request(uri, datastore['FILENAME'])
       return
     end