<svg xmlns="http://www.w3.org/2000/svg">
<defs>
<!-- check that WebKit doesn't crash, if an effect is not available in feMerge -->
<filter id="filter" primitiveUnits="objectBoundingBox">
<feMerge>
<feMergeNode in="does-not-exist"/>
</feMerge>
</filter>
</defs>
<g filter="url(#filter)"/>
<rect x="0" y="0" width="100" height="100" fill="green"/>
</svg>