1×1 matrix 0 appears positive definite and cholesky doesn't fail

When an MMatrix or SMatrix is of dimension 1-by-1, it is detected as being positive definite even if its entry is 0, and its cholesky decomposition does not fail. Below I'm using StaticArrays v1.6.5 and julia v1.9.2.

julia> using LinearAlgebra, StaticArrays

julia> m = MArray{Tuple{1,1}}(0.0); # 1×1 MMatrix

julia> isposdef(m) # should be false
true

julia> isposdef(cholesky(m)) # also true: cholesky didn't fail
true

julia> cholesky(m).info # 0 so it's supposedly PosDef
0

same with an SMatrix:

julia> s = SArray{Tuple{1,1}}(0.0);

julia> isposdef(s)
true

julia> isposdef(cholesky(s)) # doesn't fail
true

Things are as expected if the 1×1 matrix has a negative entry, or it it's a regular matrix:

julia> isposdef(MArray{Tuple{1,1}}(-1.0))
false

julia> isposdef([0.0;;])
false

Start with the 1×1 MArray and SArray reproductions in the issue, then compare their isposdef and cholesky behavior with the regular 1×1 matrix example. Trace the StaticArrays path involved in these operations and add or run a regression check showing that a zero entry is not positive definite and that cholesky does not report success.