AFF4_object_blocksize() fails to report 4KB sectors

To reproduce:

I have been testing 4KB sector support in AFF4-CPP-Lite.

To do this, I created a small disk with 4KB sectors, imaged it using XWF to an E01 file and then converted that to AFF4 using Evimetry. I can see that the 4KB sectors were correctly detected when the E01 was created (in the E01 metadata and the log file) and similarly when Evimetry generated the AFF4 file (in the metadata and the log file). However, when I checked this with the new(ish) AFF4_object_blocksize() method I found that it returns an error. I traced through the code and found that the internal properties collection only seems to contain 2 items and the block size wasn’t one of these.