fix detecting multiple figures in a log line
fix detecting multiple figures in a log line

When logging more than one figure in a single `log.user`, which happens when
using multiple image types in `config.imagetype`, the viewer didn't pick up any
figure and presented ordinary anchors instead.  This patch fixes the issue by
dropping the only-child limitation when searching for eligible figures.

nutils/nutils,joostvanzwieten/nutils,CVerhoosel/nutils,wijnandhoitinga/nutils