Segfault in detect_unbound_args with VarArg in signature

[Keno]

julia> using Test

julia> module FooAmbig
       _totuple(::Type{Tuple{Vararg{E}}}, itr, s...) where {E} = E
       end
Main.FooAmbig

julia> detect_unbound_args(FooAmbig; recursive=true)

signal (11): Segmentation fault: 11

Causing problems on #25261, but seems to be independent of it.

[vtjnash]

dup #24460