adding for loop on list to to handle the return of none when the list is empty.…

adding for loop on list to to handle the return of none when the list is empty. With the previous method if the list was empty the script died. See http://stackoverflow.com/questions/18852324/typeerror-sequence-item-0-expected-string-nonetype-found

plugins/inventory/ec2.py

@@ -622,8 +622,8 @@ class Ec2Inventory(object):
                 for group in value:
                     group_ids.append(group.id)
                     group_names.append(group.name)
-                instance_vars["ec2_security_group_ids"] = ','.join(group_ids)
-                instance_vars["ec2_security_group_names"] = ','.join(group_names)
+                instance_vars["ec2_security_group_ids"] = ','.join([str(i) for i in group_ids])
+                instance_vars["ec2_security_group_names"] = ','.join([str(i) for i in group_names])
             else:
                 pass
                 # TODO Product codes if someone finds them useful