mutool draw: empty output on some PDFs

When trying to render pages from a PDF file that makes use of Separation color spaces (a standard PDF feature) into bitmaps, "mutool draw" generates error messages:

> $ mutool draw -o output.png mutool_draw_bug_example.pdf
> page mutool_draw_bug_example.pdf 1error: Cannot convert between incompatible pixmaps
> warning: Ignoring error during interpretation
> error: Cannot convert between incompatible pixmaps
> error: Cannot convert between incompatible pixmaps
> warning: Ignoring error during interpretation
> [...some more repetitions of the same messages...]

An output file is still created, but it's empty (all white) and thus not useable.

An example document is attached to this report.

Only "mutool draw" is affected by the issue; displaying affected files with "mupdf" or rendering them with "mutool convert" works fine.

This is happening on both Ubuntu 18.04 (MuPDF 1.12) and 19.04 (MuPDF 1.14). Other versions have not been tested.

The issue does *not* occur when compiling any version of the upstream sources from scratch, even with the USE_SYSTEM_LIBS and USE_SYSTEM_LCMS2 options set. This is still the case when applying the patches from the Debian source package to the upstream sources.
However, when trying to build the Debian source package itself (using debhelper), I always end up with a non-functional version, even when disabling the USE_SYSTEM_LIBS and USE_SYSTEM_LCMS2 options for these builds. This is why I'm reporting the issue here and not upstream, as it seems to have been introduced during packaging.