Invalid validation once you try to untrack a content type

Problem/Motivation

If you have a content type configured to use this module and you uncheck the ' Limit the amount of revisions for this content type' option and save the content type you will see a message like this:

Notice: Undefined index: node in _node_revision_delete_form_node_type_submit() (line 216 of /Users/adriancid/Sites/drupal7-test/sites/all/modules/node_revision_delete/node_revision_delete.module).
Notice: Trying to get property of non-object in _node_revision_delete_form_node_type_submit() (line 216 of /Users/adriancid/Sites/drupal7-test/sites/all/modules/node_revision_delete/node_revision_delete.module).

Proposed resolution

Change the line:

elseif (!$form_state['node']->is_new) {

to

elseif (!isset($form_state['complete form']['#node_type']->is_new) || !$form_state['complete form']['#node_type']->is_new) {

Remaining tasks

None.

User interface changes

None.

API changes

None.

Data model changes

None.