Fix issue-7295

Author: nixawk

modules/exploits/unix/webapp/sugarcrm_unserialize_exec.rb

@@ -95,7 +95,7 @@ def exploit
       'data'   => data
     })
 
-    if res.nil? || res.headers['Location'].include?('action=Login') || res.get_cookies.empty?
+    if res.nil? || res.headers['Location'] && res.headers['Location'].include?('action=Login') || res.get_cookies.empty?
       fail_with(Failure::NoAccess, "#{peer} - Login failed with \"#{username}:#{password}\"")
     end