avoid division by zero in svd(::Diagonal) (#1150)

Fixes #1149

Author: araujoms

src/diagonal.jl

@@ -1024,8 +1024,8 @@ function svd(D::Diagonal{T}) where {T<:Number}
     Vt = copy(U)
     for i in 1:length(d)
         j = piv[i]
-        U[j,i] = d[j] / S[i]
-        Vt[i,j] = one(Td)
+        U[j,i] = iszero(d[j]) ? oneunit(Td) : d[j] / S[i]
+        Vt[i,j] = oneunit(Td)
     end
     return SVD(U, S, Vt)
 end

test/diagonal.jl

@@ -463,7 +463,8 @@ Random.seed!(1)
         end
     end
 
-    @testset "svd (#11120/#11247)" begin
+    @testset "svd (#11120/#11247/#1149)" begin
+        D[1] = 0
         U, s, V = svd(D)
         @test (U*Diagonal(s))*V' ≈ D
         @test svdvals(D) == s