Enabling Universal Search experiment prevents to access any webpage in address bar

[khalid32]

[Affected Version]:

Nightly 51.0a1

[Affected Platforms]:

Ubuntu 16.04, Linux 4.4.0-31-generic

[Prerequisites]:

Test Pilot is installed from https://testpilot.stage.mozaws.net/

[Steps to reproduce]:

1. Go to https://testpilot.stage.mozaws.net/experiments
2. Navigate to Enable the "Universal Search" experiment page.
3. Chose to enable universal search.
4. Then go to new tab, type any URL of a web-page in address bar and press ENTER

[Expected Result]: The experiment is successfully enabled and able to show the web page of given URL

[Actual Result]: The experiment is successfully enabled but no response showed in the address bar

[Notes]: This issue only occurs when enabling "Universal Search" experiment.

[lissyx]

dupe of #286