flutter_svg/example/assets/simple/empty_defs.svg

<svg xmlns="http://www.w3.org/2000/svg"
     width="5"
     height="3"
     viewBox="0 0 5 3">
    <defs/>
    <path id="black_stripe"
          fill="#abcdef"
          fill-opacity="1"
          fill-rule="nonzero"
          stroke="none"
          visibility="visible"
          d="M 0 0 L 5 0 L 5 3 L 0 3 Z" />
</svg>