[CUSPARSE] Fix constructor of sparse empty matrices

[amontoison]

• A.rowPtr should always be [1] for empy matrices in CSR format.
• A.colPtr should always be [1] for empy matrices in CSC format.
  We want to ensure A.rowPtr[end] == nnz(A) + 1 and A.colPtr[end] == nnz(A) + 1.

The display issue in #2570 is related.

[maleadt]

CI failure looks related:

libraries/cusparse/conversions: Error During Test at /var/lib/buildkite-agent/builds/gpuci-11/julialang/cuda-dot-jl/test/libraries/cusparse/conversions.jl:42
  Got exception outside of a @test
  CuArray only supports element types that are allocated inline.
  Any is not allocated inline