Fatal error on cancel action for new activity after new contact is created

for tracking: http://dev.nysenate.gov/issues/5007

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1) Fatal error on cancel action
Steps to replicate:
a. Go to New Activity ( standalone mode )
b. Create new "With Contact" using contact popup
c. Click on "Cancel" button on activity form. It throws fatal error.

2) Also if we create an activity and then create a contact from within it, redirect to newly created contact if we then cancel the activity. But if we don't create a contact, we should just return to the previous page.