Avoid extra array allocation for where(x: [...])

We do not need to construct an array of `nil`s; we merely need to
determine whether any are present in the values array and remove them.
Thus, we can use `compact!` instead of `extract!`.

activerecord/lib/active_record/relation/predicate_builder/array_handler.rb

@@ -13,7 +13,7 @@ def call(attribute, value)
         return attribute.in([]) if value.empty?
 
         values = value.map { |x| x.is_a?(Base) ? x.id : x }
-        nils = values.extract!(&:nil?)
+        nils = values.compact!
         ranges = values.extract! { |v| v.is_a?(Range) }
 
         values_predicate =
@@ -23,7 +23,7 @@ def call(attribute, value)
           else Arel::Nodes::HomogeneousIn.new(values, attribute, :in)
           end
 
-        unless nils.empty?
+        if nils
           values_predicate = values_predicate.or(attribute.eq(nil))
         end