edx/edx-platform — pull request #3892 by louyihua (2014-05-28 05:14:37+00:00)
Title: Fix exception on Internet Explorer when adding first transcript language

Internet Explorer throws an "Invalid arguement" exception when uses an empty string as the parameter in ```namedItem``` method.
As other browsers returns ```null``` when the parameter is an empty string, it is safe to first test whether the parameter is an empty string, and if not then the original code is executed.