Non-base64 data-URI are returned

[s0ph1e]

Need to skip similar data URIs:

img.grayscale {
    filter: url("data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg'><filter ….2525 0 0 0.2525 0.2525 0.2525 0 0 0 0 0 1 0'/></filter></svg>#grayscale");
    filter: url("data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg'><filter id='grayscale'><feColorMatrix type='matrix' values='0.3333 0.3333 0.3333 0 0 0.3333 0.3333 0.3333 0 0 0.3333 0.3333 0.3333 0 0 0 0 0 1 0'/></filter></svg>#grayscale");
    filter: gray;
    -webkit-filter: grayscale(100%);
    -webkit-backface-visibility: hidden
}