CLN: remove unneeded try/except in nanops
Look like this try/except isn't needed, checking in CI if it verifies the result.
I rearranged it again. `if (axis is not None and values.shape[axis] == 0) or values.size == 0:` is always the same as `if values.size == 0:` AFAIKT.

So I've just added a `if values.size == 0` clause at the top and cleaned up even further, so it's quite simple now. Thanks @topper-123 