Hello, small fix to HTTP calls appending 'undefined' to URL

[nukleas]

Hello,

I was trying to make calls to dx.doi.org 's site using Extendables, but I noticed an appending of "undefined" to the end of my called URL, which would then cause the site to give me a 'DOI not found' error. I seemed to find the place where this was happening, and I made it so that if url.search was undefined, it would default to a blank string, which wouldn't affect the HTTP call.

Hopefully this change is useful,

Nukleas

... (url.search was undefined, would concatenate undefined to end of url)