ElfLoader: Don't scan for functions in zero-length sections

[hrydgard]

This section has both GetSectionAddr and GetSectionSize returning 0.

			u32 start = reader.GetSectionAddr(id);
			// Note: scan end is inclusive.
			u32 end = start + reader.GetSectionSize(id) - 4;
			u32 len = end + 4 - start;

We end up with start = 0, end = 0xFFFFFFFC, len = 0 and Memory::IsValidRange returning true because len = 0 due to wraparound.

So we try to scan 0 to 0xFFFFFFFFC for functions, which causes problems.

Happens in WWE: Smackdown Vs Raw 2009 during initial load.

Fixes #12414 again (somewhat different problem this time).

[unknownbrackets]

This makes sense. Almost feels like GetCodeSections() shouldn't return sections that wouldn't be mapped to memory (i.e. sh_size != 0 or sectionAddrs[x] == 0. I guess this executable wasn't set to relocate, and had sh_addr == 0? Seems like we're probably outputting bad logs for this ELF.

-[Unknown]

[hrydgard]

Yeah, we can probably clean this up quite a bit. Didn't do it because I wanted a minimal fix for the release, of course - more appropriate to do later.