Empty file compressed to hdt is not encoded correctly

[D063520]

If we take an empty n-triple file then the corresponding hdt file is not encoded correctly. This is noticeable if the corresponding file is opened in hdt-java. The following comment described the problem in the hdt file:

rdfhdt/hdt-java#31 (comment)

When opening the hdt file one will notice that here:

hdt-cpp/libhdt/src/sequence/AdjacencyList.cpp

Line 37 in 332a9cc

elements(el),

the el and bit have a length of respectively 0 and 1. But both should be 0!!! Where exactly this is encoded is not clear to me and needs to be debugged in this repo.