I am using
\externalfigure[filename.png] to display PNG files in my document in ConTeXt, e.g.:
\starttext \externalfigure[001.png] \stoptext
Sometimes the file is not found. In this case, ConTeXt compiles, but displays a large gray space on the page where the image would be.
How can I get ConTeXt to print absolutely nothing there in the place where an image should be, in the event that the image file is missing?