Just a bunch of fixes

[dodomorandi]

These are just some bugs I found thanks to warnings and sanitizers.

Unfortunately there are quite a lot of misalignment issues related to how memory is allocated (for instance using `R_FrameAlloc) causing UB -- luckly enough this should not be a major issue for x86/x86_64 platforms that support unaligned accesses.

There are also some null pointer dereferencing (here for instance, where ac can be null), but honestly I am not sure how some of these situations should be handled.