Fix for imageTV access denied

When you select an imageTV the file is not loaded.
This happens only with MODX 2.3 (latest nightly).

When loading a resource in the manager the imageTV src is this (loaded correctly):
`http://site/system/phpthumb.php?h=150&w=150&src=image.jpg&source=1`

But when you create/change the imageTV you get an access denied:
`http://site/connectors/index.php?action=system/phpthumb&h=150&w=150&src=image.jpg&wctx=web&source=1`

_{"success":false,"message":"Access denied.","total":0,"data":[],"object":{"code":401}}_