fix struts_code_exec_exception_delegator - NoMethodError undefined method 'empty?' for nil:NilClass

modules/exploits/multi/http/struts_code_exec_exception_delegator.rb

@@ -186,7 +186,7 @@ class MetasploitModule < Msf::Exploit::Remote
   end
 
   def exploit
-    if not datastore['CMD'].empty?
+    if !datastore['CMD'].blank?
       print_status("Executing user supplied command")
       execute_command(datastore['CMD'])
       return