Fix anytracedarray override

[wsmoses]

hopefully fixes the sort issue

Fix #1231, fix #1286.

[mofeing]

Im out of town and won't be able to access my laptop until Sunday, but if methods(sort, (Vector{Union{}},)) doesn't show the reactant method and sort(Vector{Union{}}()) doesn't crash, then everything should be fine.

[wsmoses]

indeed all is well:

julia> using Reactant
Precompiling Reactant finished.
  1 dependency successfully precompiled in 16 seconds. 55 already precompiled.

julia> Vector{Union{}} <: Reactant.AnyTracedRArray
false

julia> methods(sort, (Vector{Union{}},))
# 1 method for generic function "sort" from Base:
 [1] sort(v::AbstractVector; kws...)
     @ Base.Sort sort.jl:1489

julia> sort(Vector{Union{}}())
Union{}[]

julia>