Recent font problem

Hi Heinrich :)

Just in the last two git pulls I've been seeing pan closing with an
assertion in cairo, but today I also got these pango complaints:

Pango-CRITICAL: pango_font_description_set_size: assertion 'size >= 0' failed

Pango-WARNING: failed to create cairo scaled font, expect ugly output, the
offending font is 'Cantarell'

Pango-WARNING: font_face status is: no error has occurred

Pango-WARNING: scaled_font status is: invalid matrix (not invertible)

Pango-WARNING: shaping failure, expect ugly output, shape-engine='BasicEngineFc',
font='Cantarell', text="Connecting'

pan: cairo-surface.c:1287: cairo_surface_set_device_offset: Assertion 'status ==
CAIRO_STATUS_SUCCESS' failed

I also recently 'upgraded' to gnome 3, which uses Cantarell as its default font.

This error doesn't happen all the time.  I've seen it mostly while pulling headers
from a busy binary group with bazillions of headers, but I doubt the number of
headers has anything to do with this problem.  Maybe some weird character in one
of the headers?

To add to the confusion, I just now finally updated that group without problem,
so I dunno if I can reproduce it again.  Yesterday the assertion was 100% in the
one problem group, but I don't recall it in any other groups.  I'll let you know
if the problem recurs again tomorrow.

Any ideas?

Many thanks!