Ensure that the size functions won't return negative numbers

[moble]

If the user accidentally asks for an $\ell=0$ component when $s=0$, for example, Ysize(ℓₘᵢₙ, ℓₘₐₓ) can be called with ℓₘᵢₙ > ℓₘₐₓ, and a negative size is returned. At best, this causes an ArgumentError: invalid GenericMemory size: too large for system address width.