[poppler] invalid option can cause SEGV in pdftocairo

[suzuki toshiya]

Albert Astals Cid wrote:
>> If endDocument() is invoked without beginDocument(), uninitialized
>> surface and output_file are referred, therefore, SEGV is caused.
>>
>> The easiest fix would be NULL-initialization (not needed in C++?) of
>> surface & output_file, and checking NULL before referring them in
>> endDocument(). Patch is attached.
> 
> I'd prefer an if check for lastPage < firstPage that tells the user to not 
> give the program bad parameters. Can you work on that?

OK, I will do so. Although SEGV does not occur, other utilities
(e.g. pdftotext, pdftoppm, pdftops etc) do not check such. I will
make a patchset for all pdftoXXX utilities.

> Cheers.
>   Albert
> 
>> Regards,
>> mpsuzuki
>