NullPointerException on Tern Node.js Preference page

Issue is fixed

Signed-off-by: vrubezhny <vrubezhny@exadel.com>
Bug: https://github.com/angelozerr/tern.java/issues/28
Merge pull request #29 from vrubezhny/NPEinTernNodeJSPrefPage

NullPointerException on Tern Node.js Preference page

Stupid error-( Thank's Victor!