Svgo: Empty `defs` added

[XhmikosR]

I was trying to see if https://github.com/alrra/browser-logos/blob/a1f2645fce1ac1e41c2bca34f3fc4be89a376941/src/edge/edge.svg from (https://github.com/alrra/browser-logos/pull/180) was run through SVGOMG.

When I enabled the option Replace duplicate elements with links, I noticed an empty <defs/> being added. Maybe there should be a sanity check for this?

I believe SVGOMG is using v1.3.0, so bear with me if this is something fixed after 1.3.0.

[ChrisRu]

Correct, a simple SVG without any use elements like:

<svg viewBox="0 0 200 200" xmlns="http://www.w3.org/2000/svg">
    <text>
        text element
    </text>
</svg>

Now produces

<svg viewBox="0 0 200 200" xmlns="http://www.w3.org/2000/svg">
    <defs/>
    <text>
        text element
    </text>
</svg>

and the element is not needed for rendering.