Don't transpose empty MtlArrays (#658)

* Don't transpose empty MtlArrays

* Add test

Author: christiangnrd

src/linalg.jl

@@ -245,6 +245,8 @@ end
                                                    A::MtlMatrix{T}) where {T}
     axes(B, 2) == axes(A, 1) && axes(B, 1) == axes(A, 2) || throw(DimensionMismatch("transpose"))
 
+    isempty(B) && return B
+
     M, N = size(A)
     dev = device()
     queue = global_queue(dev)

test/linalg.jl

@@ -108,4 +108,12 @@ using Metal: storagemode
     @test storagemode(lua.factors) == storagemode(lua.ipiv) == storagemode(A)
 end
 
+@testset "transpose" begin
+    A = MtlMatrix(rand(Float32, 0, 1024))
+    B = Metal.zeros(Float32, 1024, 0)
+
+    # Issue #656
+    @test isempty(transpose!(B, A))
+end
+
 end