In-Portal has Auto-Complete features in some places, where it already knows what user wants to type. One of such places is suggestion of E-mail Template Name in the "Website & Content > E-mail Templates" section. Suggestion works flawlessly, but due incorrect object usage (missing array('skip_autoload' => true) part during object creation) the "Requested ID for prefix email-template not passed" notice is thrown each time the OnSuggestValues event (which powers auto-complete feature) is used.
When fixing keep in mind, that this event was rewritten in In-Portal 5.3.x branch to allow usage of jQuery.Autocomplete component in Admin Console.