REPL: Completion on a LOAD_PATH mutation breaks LOAD_PATH

[IanButterworth]

Note the #undef after the completion is generated here.

julia> Base.active_repl.options.hint_tab_completes = false
false

julia> LOAD_PATH
3-element Vector{String}:
 "@"
 "@v#.#"
 "@stdlib"

julia> append!(empty!(LOAD_PATH),<tab>
append!(a::Vector{T}, items::Union{Tuple, AbstractVector{<:T}}) where T @ Base array.jl:1349
append!(a::AbstractVector, iter) @ Base array.jl:1357
append!(a::AbstractVector, iter...) @ Base array.jl:1359
julia> append!(empty!(LOAD_PATH),^C

julia> LOAD_PATH
3-element Vector{String}:
 #undef
    "@v#.#"
    "@stdlib"

Doesn't happen here

julia> x = [1, 2, 3]
3-element Vector{Int64}:
 1
 2
 3

julia> append!(empty!(x),<tab>
append!(a::Vector{T}, items::Union{Tuple, AbstractVector{<:T}}) where T @ Base array.jl:1349
append!(a::AbstractVector, iter) @ Base array.jl:1357
append!(a::AbstractVector, iter...) @ Base array.jl:1359
julia> append!(empty!(x),^C

julia> x
3-element Vector{Int64}:
 1
 2
 3

Happens on b1fffb0 and #57767

[topolarity]

@aviatesk might know what's going on here