dispatch.c: Fix dispatching of empty files when num_entries < num_parts
dispatch.c: Remove dead code (num_empty_entries)
file_entry.c: Avoid closing fd -1
add_* functions: Remove never-reached/useless init of head
utils.h: Align str_is_negative() prototype with implementation
fpart.c: Typo
Update changelog regarding recent bugs spotted by Claude (Anthropic)
file_entry.c: Replace signal() calls by sigaction() ones