Minor JavaScript fix

Summary: Currently, `editdata` is implicitly defined as a global variable (and JSHint complains about this). Instead, change it to be a local variable.

Test Plan: `arc lint` showed one less warning.

Reviewers: #blessed_reviewers, epriestley

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D11062