Contextual filter + "Display PDF in browser" disabled causes pdf's to be downloaded without file names and with an incorrect file extension

Hi all,
This is mainly an issue with IE (11), as Chrome and Mozilla come with built in pdf viewers that would have to be manually disabled for this bug to affect them.

I'm using pdf view to display webform content contextually filtered by sid. The view works fine if "Display PDF in browser" is enabled in Adobe Acrobat/Acrobat Reader > Edit > Preferences > Internet. But if adobe's "Display PDF in browser" preference is disabled, when viewing the pdf view, the pdf will download as ".pdf[2]".

I tried on both 1.4 and 1.x dev, with the same result.