slight simplification: use optional arg (#5)

Author: nsajko

src/ZeroDimensionalArrays.jl

@@ -116,11 +116,7 @@ for Arr ∈ (
     end
 end
 
-function ZeroDimensionalArrayMutable{T}(::UndefInitializer) where {T}
-    new_zero_dimensional_array_mutable_undef(T)
-end
-
-function ZeroDimensionalArrayMutable{T}(::UndefInitializer, ::Tuple{}) where {T}
+function ZeroDimensionalArrayMutable{T}(::UndefInitializer, ::Tuple{} = ()) where {T}
     new_zero_dimensional_array_mutable_undef(T)
 end