Add a test and correct a typo

Author: pabloferz

base/broadcast.jl

@@ -343,7 +343,7 @@ the following rules:
    (and treats any `Ref` as a 0-dimensional array of its contents and any tuple
    as a 1-dimensional array) expanding singleton dimensions.
 
-The following additional rule apply to `Nullable` arguments:
+The following additional rule applies to `Nullable` arguments:
 
  - If there is at least a `Nullable`, and all the arguments are scalars or
    `Nullable`, it returns a `Nullable` treating `Nullable`s as "containers".

test/broadcast.jl

@@ -409,3 +409,9 @@ Base.Broadcast.broadcast_c(f, ::Type{Array19745}, A, Bs...) =
     @test isa(aa .+ 1, Array19745)
     @test isa(aa .* aa', Array19745)
 end
+
+# broadcast should only "peel" one container level
+let io = IOBuffer()
+    broadcast(x -> print(io, x), [Nullable(1.0)])
+    String(take!(io)) == "Nullable{Float64}(1.0)"
+end