Inconsistent treatment of zero-length arrays in concatenation

[BioTurboNick]

Raised in #41047 and related to other concatenation consistency issues #38019 (mixed scalars and arrays) and #40111 (dimensionality of empty arrays returned by concatenation methods).

Concatenation of zero-length arrays does not behave consistently across methods.

[[] [] ; 4 5] => [4 5]

[[] [] 4 5] => DimensionMismatch("mismatch in dimension 1 (expected 0 got 1)")

[[]; []; 4; 5] => [4; 5]

[[]; 4 5] => ArgumentError: number of columns of each array must match (got (1, 2))

[[] []; 5] => ArgumentError: number of columns of each array must match (got (2, 1))

[[] 4 ; [] 5] => DimensionMismatch("mismatch in dimension 1 (expected 0 got 1)")

[4 []; [] 3] => DimensionMismatch("mismatch in dimension 1 (expected 1 got 0)")

[[] []; [] []] => 0×2 Matrix{Any}

[BioTurboNick]

Looking more closely, I see it acts as if it is size == (0, 1, 1...), which is maybe a bit weird on the surface, but not actually inconsistent.