Fix one, break one

[Hans Ronne]

>I've checked in the following change.  Not sure whether it is quite
>right, as the reason for calling add_shrunken_image twice (or in fact,
>what about add_shrunken_image is stateful) is not clear.

Excellent. It fixes the recent crashes. The reason for calling
add_shrunken_image twice is that imfapp, which I just gave a major
overhaul, displays images at four different magnifications. It would fail
to do the smallest one (8x8) correctly without the second call for images
that were only available at 32x32 resolution.

Hans