find(x::Array{Nullable{Bool}}) gives useless results

[nalimilan]

The behavior of find on Array{Nullable{Bool}} doesn't make any practical sense:

julia> x = [Nullable(true), Nullable(false)]
2-element Array{Nullable{Bool},1}:
 Nullable(true) 
 Nullable(false)

julia> find(x)
2-element Array{Int64,1}:
 1
 2

# Reason:
julia> Nullable(false) != 0
true

There's a special method for find(::NullableArray) which returns the expected result, but it doesn't sound great that arrays of Nullable{Bool} don't behave properly. Should Nullable(false) != 0 be equivalent to false != 0?

(This is a bit weird to report this against this repo, but since ==(::Nullable, ::Nullable) is defined here...)