When deleting whole line, deletes per-line data (annotations, line state etc) from next line, not from the deleted line.
It is because void LineVector::RemoveLine(line) is called with 1-based line index, and it calls perLine->RemoveLine(line), which must be called with 0-based line index.
To fix: in LineVector::RemoveLine insert line--.
Related: when the range being deleted begins at the end of a line (eg when deleting last empty line (just \r\n)), deletes per-line data of that line. Should delete data of next line. But this is not so important.