edge: Fix data block decoder (Coverity)

Use a signed integer instead of an unsigned one for num_chunks
which can set to a negative value on error.

Ensure that chunks is not dereferenced if it is NULL. In fact
that will not happen currently, since num_chunks is now always
<= 0 if chunks == NULL.

Fixes: Coverity CID 1347433, 1347434, 1347435

Sponsored-by: On-Waves ehf
1 file changed