Update startup.js
Update startup.js

Showing the download link in showDownload button view checks the following 
Modernizr tests to pass

Modernizr.download && Modernizr.bloburls && Modernizr.blobbuilder

In the Else condition , it expects the download iFrame should be present , else
throwing uncaught JS exception.

So the same check should be here also for creating the iFrame.
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