check for null surface in test

If the bounds of the blob are empty, we will request a zero-sized surface
which will fail. Just check for that.

Only expect this if the typeface is empty (e.g. faked out for testing)

Bug: skia:
Change-Id: Idcac0e9d4e2a5fe68926a33250015609b5c7e365
Reviewed-on: https://skia-review.googlesource.com/22360
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Mike Reed <reed@google.com>
1 file changed