Fixed minor typo which prevents feed items & mapped entities from deleti...

## Ready State: Yes

Relates to jira task: https://imagex.atlassian.net/browse/LDC-315

Found new error when deleting aggregator items, original data type mismatch error remains.

## Requirements & Dependencies

None

## Deployment Instructions

* Merge code.
* Enable module `imagex_aggregator`
* Clear caches with `drush cache-clear all`

## Usage/Test Instructions

* Go to /admin/config/services/aggregator & add a feed, just map to a node type & fields, title -> title
* Back on /admin/config/services/aggregator, click "Update Items" on feed, ensure "ITEMS" column updates & that the ensure a related node (of the type selected) has been created for each feed item
* Next click the "remove items" link and delete all items, ensure:
 * no errors are shown
 * aggregator items & related nodes are deleted