comark/xref/missing-id

:ref reads the id it points at from {#...}. Without one, it has nothing to number and renders as [?]. Writing the label without its # makes it a prop instead of an id, so the reference still names nothing.

![Three ducks on the pond](ducks.png){#fig-ducks}

As :ref{fig-ducks} shows, the ducks stay near the reeds.

![Three ducks on the pond](ducks.png){#fig-ducks}

As :ref{#fig-ducks} shows, the ducks stay near the reeds.