Confirming I'm seeing this same bug.
$> convert -background transparent -fill black -pointsize 32 label:test out.png
convert.im6: no images defined `out.png' @ error/convert.c/ConvertImageCommand/3044.
$> convert -version
Version: ImageMagick 6.7.7-10 2016-11-29 Q16 http://www.imagemagick.org Copyright: Copyright (C) 1999-2012 ImageMagick Studio LLC Features: OpenMP
Ubuntu 14.04
$> lsb_release -a
No LSB modules are available. Distributor ID: Ubuntu Description: Ubuntu 14.04.5 LTS Release: 14.04 Codename: trusty
Confirming I'm seeing this same bug.
$> convert -background transparent -fill black -pointsize 32 label:test out.png
convert.im6: no images defined `out.png' @ error/convert. c/ConvertImageC ommand/ 3044.
$> convert -version
Version: ImageMagick 6.7.7-10 2016-11-29 Q16 http:// www.imagemagick .org
Copyright: Copyright (C) 1999-2012 ImageMagick Studio LLC
Features: OpenMP
Ubuntu 14.04
$> lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 14.04.5 LTS
Release: 14.04
Codename: trusty