Fix so workbench access doesn't fire a notice when certain content items are created (see LDC 431)

## Ready State: Yes

This pull request related to the following JIRA tickets:

[LDC-431: PHP Errors when creating new Blog (and other) content](https://imagex.atlassian.net/browse/LDC-431)

## Requirements & Dependencies

* No Requirements at this time.

## Deployment Instructions

* Merge code

## Usage/Test Instructions

* Fixes issue where creating some nodes fires a notice the the $node->workbench_access variable isn't set.  This fix ensures that the variable is set before trying to do anything with it.

* NOTE: Not sure if I'm going about this the correct way, feedback appreciated, might discuss with Kevin Champ and he's the originator of this patch.