Unnecessary null checks before freeing

[ariccio]

I have:

• searched open and closed issues for duplicates

---

Bug description

I was just reading through the code as a matter of curiosity - I've always loved signal, and wanted to see the C implementation - and noticed that you're checking if a pointer is null many times before freeing them. This is perfectly valid, but absolutely not necessary, as free always checks for this on it's own. It thus leads to unnecessary code bloat. Nothing wrong with saving a few bytes!

Actual result: extra generated code, thus extra bloat.

Edit: see signal_protocol.c for examples.