little auto detect fix

Author: Michael Messner

modules/exploits/linux/http/dlink_dspw215_info_cgi_rop.rb

@@ -71,6 +71,10 @@ def check
                 break
               end
             end
+
+          else
+            # no supported device found
+            return Exploit::CheckCode::Unknown
           end
 
           print_status("#{peer} - Selected Target: #{@mytarget.name}")