Problem with private webform fields

I would like to pass some information to sugar from this form but I don't want the user to see it, e.g.: lead_source is website form #x.

I though I could use the private option in the webform field, so i created a textfield and added the text to the default option, and set it to private. I have matched this field with the correct field in sugar using the webform2sugar tab.

The problem is that on submission the form generates an error:

Notice: Undefined index: 7 in webform2sugar_webform_submission_insert() (line 94 of /home/podsystem/public_html/sites/all/modules/webform2sugar/webform2sugar.module).
Warning: array_key_exists() expects parameter 2 to be array, null given in webform2sugar_webform_submission_insert() (line 94 of /home/podsystem/public_html/sites/all/modules/webform2sugar/webform2sugar.module).
Notice: Undefined index: 7 in webform2sugar_webform_submission_insert() (line 97 of /home/podsystem/public_html/sites/all/modules/webform2sugar/webform2sugar.module).
Warning: Invalid argument supplied for foreach() in webform2sugar_webform_submission_insert() (line 102 of /home/podsystem/public_html/sites/all/modules/webform2sugar/webform2sugar.module). 

And the information is not saved in sugar, if I set this field to not private everything works fine.

Any help?

Thanks!