Fix CodeQl overflow warnings

[ann0see]

We're building Opus via our CI with CodeQl and it seems to give overflow warnings - although they might be invalid:

It would be good to investigate (and potentially fix them)?

[silverbacknet]

I haven't checked all of them, but all of the ones I've looked at are logically just completely impossible to overflow, they're always working with small numbers. A handful of overflows have been found and fixed over the years, but these don't seem to qualify?

[ann0see]

Probably? I don’t know the code but I found it very annoying to see it in CodeQL, so I opened this issue. Do you think anything can be done to fix it