Uncaught TypeError breaks site Javascript

D7 installation. When I install the module, both ckeditor and Module Filter stop working.
My Javascript console shows an "Uncaught TypeError: Cannot read property 'length' of null " in external-iframe/js/external_iframe.js line 38

The offending line is:
if (parent.length > 0) {

Before configuration is completed, the db returns null for the parent selector. So when the script returns a null object, this line breaks = and because the exception isn't caught, all further scripts on the page also break.

Solution:
We need to verify the parent property before we get to this point. Also on the configuration page, pre-fill "Enter parent container for where External Iframe should search for and rewrite external links" with something, anything. Nowadays, the average Drupal admin doesn't know much about js identifiers.