Plans: Assignment Portfolio preview is producing console error

[Lisa Seeto]

A warning and a console error are currently being produced when attempting to view an Assignment preview when adding a new task to a plan.

Steps to reproduce:
1. Log in and create a new collection of at least one page (page/s can be blank)
2. Create a new plan (Create-> Plans), set "Template" to 'yes' and "Assignment tasks" to 'yes'
3. Open the 'Developer Tools' console (on Firefox press F12, on Chrome press CNTRL+SHFT+J) and navigate to the 'Console' tab
4. Add a 'New task' to the plan and on 'Assignment portfolio' drop down select the collection and click to preview it. Inspect the console in the developer tools.
Expected:
The console is clear of errors.
Actual:
The console displays the following error:
"Uncaught ReferenceError: collection_nav_init is not defined" (from code called in new.php -> previewcollectionnav.tpl)
5. Refresh the page
Expected:
The page displays correctly with no warnings
Actual:
The page displays with warning messages:
".../dwoo/compile/raw/0137da1da5ce3bb7b6f4779e5dd77aab.d136.php:39) count(): Parameter must be an array or an object that implements Countable" (See the screenshot attached for details)