[ITensors] Add checkflux debug check to factorize (#1307)

src/tensor_operations/matrix_decomposition.jl

@@ -763,6 +763,7 @@ function factorize(
   (singular_values!)=nothing,
   dir=nothing,
 )
+  @debug_check checkflux(A)
   if !isnothing(eigen_perturbation)
     if !(isnothing(which_decomp) || which_decomp == "eigen")
       error("""when passing a non-trivial eigen_perturbation to `factorize`,