Null check PrimaryFont().

No known way to reproduce, but this null check fixes a crasher reported
to the Opera crash servers for the desktop version of Opera. There was
already a null check for PrimaryFont() on the first line style in the
same method. This fix has been shipped and confirmed to fix the issue
for Opera.

Only seeing crashes for Windows on our crash server, so it might be a
Windows-only issue.

R=drott@chromium.org,eae@chromium.org

Change-Id: Ifca144023a319e4b900da12c62900819ba09f777
Reviewed-on: https://chromium-review.googlesource.com/538758
Reviewed-by: Dominik Röttsches <drott@chromium.org>
Commit-Queue: Rune Lillesveen <rune@opera.com>
Cr-Commit-Position: refs/heads/master@{#480406}
1 file changed