Bug#991066: vlfeat FTBFS with imagemagick with the #987504 change

[Adrian Bunk]

Source: vlfeat
Version: 0.9.21+dfsg0-3
Severity: serious
Tags: ftbfs

https://tests.reproducible-builds.org/debian/rb-pkg/buster/amd64/vlfeat.html

...
        CONVERT doc/figures/cell-bins.png
"convert" -units PixelsPerInch -density 95 -resample 95 -trim "doc/build/figures/cell-bins.pdf" "doc/figures/cell-bins.png"
convert-im6.q16: attempt to perform an operation not allowed by the security policy `PDF' @ error/constitute.c/IsCoderAuthorized/408.
convert-im6.q16: no images defined `doc/figures/cell-bins.png' @ error/convert.c/ConvertImageCommand/3258.
make[2]: *** [make/doc.mak:213: doc/figures/cell-bins.png] Error 1


See #987504 for background.

The Ubuntu diff (linked from tracker.debian.org) seems to contain a fix.