PDF export process stops when it find a problematic object, e.g. a singular transformation matrix
#### Steps to reproduce:
<!-- Describe what you did (step-by-step) so we can reproduce: -->
- open Inkscape
- open the test file
- export to PDF
#### What happened?
I have the imported the pony SVG created outside inkscape. When I export it to PDF, inkscape stops adding objects as soon as it process the white parts around the major pink star. I created a group named "Problematic Paths" to group them.
If I change fill to a solid color (yellow), it works as expected.
I duplicated the pony twice. The original one I fixed the issue replacing the "Problematic Paths" fill with a solid yellow. I left the other two as they were imported. When I export the file, I can see the correct first object and the second object until it process the "Problematic Paths" objects, leaving an incomplete drawing. The third object is not even processed.
#### What should have happened?
It should be exported as inkscape shows it
#### Inkscape Version and Operating System:
- Inkscape Version: Inkscape 0.92.4 (5da689c313, 2019-01-14)
- Operating System: Linux
- Operating System version: Ubuntu 19.04
The original file:
[desenhando.svg](/uploads/fb193f9aaed5f3d46d544c1b9049eeec/desenhando.svg)
The exported one:
[desenhando.pdf](/uploads/769cd3eecd29e450f108a1e575b00c23/desenhando.pdf)
Edit by @jhofinger: Same problem with arcs with rx or ry=0, see #692
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