getImageURIString skips images that have query string parameters

Created by: sripathikrishnan

Some background images have query parameters in them, like this -

background-image : url('/path/to/image.png?width=64&height=64')

In such cases, the method getImageURIString(..) computes the file extension as png?width=64&height=64, and goes on to assume the URL is NOT an image.