type not set properly when is not the default name

The default node type for simplenews content is "simplenews", however, drupal allows to change every nodetype name.
This corrects that error. I don't know if you can have more than one type with the "simplenews" property, I assumed that you have just one.
If you could have more than one newsletter nodetype, then the solution should be including a selector box.
For now, this solves the problem. (inject_node function , line 417)

    $types = variable_get('simplenews_content_types', array('simplenews'));
    $node->type = array_pop($types);