When color options specified, Grunti adds color to area that should have none

[maggiewachs]

This icon is a simple line arrow, and additional colors are specified with the following file name: arrow-back.colors-ffffff-002B5C.svg.

It should look like the following:

But the SVGs generated by Grunti are showing up with a fill color when there should be none:

Sample SVG code:

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<svg width="7px" height="11px" viewBox="0 0 7 11" version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:sketch="http://www.bohemiancoding.com/sketch/ns">
    <!-- Generator: sketchtool 3.4 (356) - http://www.bohemiancoding.com/sketch -->
    <title>arrow-back</title>
    <desc>Created with sketchtool.</desc>
    <defs></defs>
    <g id="Page-1" stroke="none" stroke-width="1" fill="none" fill-rule="evenodd" sketch:type="MSPage">
        <g id="Icons" sketch:type="MSArtboardGroup" transform="translate(-655.000000, -196.000000)" stroke="#4EA8DA" stroke-width="2">
            <path d="M661.126316,197 L657,201.472163 L661.126316,205.944326" id="arrow-back" sketch:type="MSShapeGroup" fill="none"></path>
        </g>
    </g>
</svg>