Debian python-libais: libais through 0.15 VdmStream::AddLine uses an unchecked sentinel value as a vec…

libais through 0.15 VdmStream::AddLine uses an unchecked sentinel value as a vector index when processing AIS sentences with empty or out-of-range sequential message IDs. Remote attackers can crash services or vessel systems by sending crafted AIVDM sentences over VHF marine radio or IP feeds, causing out-of-bounds memory access and potential corruption.