Fix pointer underrun when allocating large vectors
Fix pointer underrun when allocating large vectors

BlueBrain/flatbuffers,BlueBrain/flatbuffers,rdumusc/flatbuffers,rdumusc/flatbuffers,rdumusc/flatbuffers,rdumusc/flatbuffers,BlueBrain/flatbuffers,rdumusc/flatbuffers,BlueBrain/flatbuffers,BlueBrain/flatbuffers,BlueBrain/flatbuffers,rdumusc/flatbuffers