Fix infinite loop with getImage

Summary: The live-editor merge missed this. See http://phabricator.khanacademy.org/D11134

Test Plan: - See http://phabricator.khanacademy.org/D11134

Reviewers: john

Reviewed By: john

Subscribers: #cs

Differential Revision: http://phabricator.khanacademy.org/D12639