PDF file opened with relative path (cli) crashes on import via poppler

Follow-up to
- Bug #1052710 “No PDF preview shown when opening PDF with an relative path”
  <https://bugs.launchpad.net/inkscape/+bug/1052710>

It appears that rev 12127 <http://bazaar.launchpad.net/~inkscape.dev/inkscape/trunk/revision/12127> undid the fix for bug #1052710, and this now triggers a crash when loading the PDF file with 'import via poppler' checked (normal import works ok).

Steps to reproduce:
1) launch current trunk with PDF file as command line argument:
$ inkscape document.pdf
2) check '[x] import via poppler' in the PDF import dialog

--> crash.

Notes:
- Preview is shown / no crash with 'import via poppler' if providing absolute path to the PDF file:
$ inkscape "$(pwd)/document.pdf"

Based on tests with archived builds on OS X 10.7.5:
- not reproduced with rev <= 13408
- reproduced with rev >= 13410
the crash itself is related to
Revision 13409: "merge pdf import via poppler-cairo into native importer"
<http://bazaar.launchpad.net/~inkscape.dev/inkscape/trunk/revision/13409>

The underlying issue seems likely to be the same as with the missing preview image (which is rendered via poppler-cairo AFAIU).

Reproduced with lp:inkscape r13484 on OS X 10.7.5 and lp:inkscape/experimental r13453 Ubuntu 14.04 (VM 64bit).