NPE in JBig2Filter if BitsPerComponent is missing

From Erik Zeiske in the mailing list:

I have an issue with PDFBox and the handling of a MRC Compressed PDF.

The issue is related to the JBIG2 Compression used in the PDF. If I
try to extract the different Images used in the PDF attached, the
library throws an NullPointerException cause the Bits are not defined
in the JBIG2-Filter. I think this is because in the PDF there is no
"Bits per Component" defined in the JBIG2-Image. If I try to define
the Bits in the JAVA-Code the program runs without an error, but it
doesn't apply the JBIG2 mask properly to the foreground-colour-image
of the PDF. To fix this issue I tried to extract the mask into a file,
but it seems like the mask-image is the same as the foreground-image.
I couldn't find the reason for this and I don't think it is related to
the PDF itself.

I haven't understood all of this (maybe it is moot after the upcoming bugfix), but one thing is sure: an NPE is thrown if BitsPerComponent does not exist.

Our code can only process bpc=1, so we can use that one as default.

Edit: I've now understood the 2nd problem, it will be handled in PDFBOX-3559.