Don't return the same object when using find with an empty array

When you pass an empty array to find we know we shoudl return an empty
array but it is surprising that we are returning the original empty
array instead of a new one.

activerecord/lib/active_record/relation/finder_methods.rb

@@ -417,7 +417,7 @@ def find_with_ids(*ids)
         raise UnknownPrimaryKey.new(@klass) if primary_key.nil?
 
         expects_array = ids.first.kind_of?(Array)
-        return ids.first if expects_array && ids.first.empty?
+        return [] if expects_array && ids.first.empty?
 
         ids = ids.flatten.compact.uniq
 

activerecord/test/cases/finder_test.rb

@@ -365,7 +365,10 @@ def test_find_by_bang_on_relation_with_large_number
   end
 
   def test_find_an_empty_array
-    assert_equal [], Topic.find([])
+    empty_array = []
+    result = Topic.find(empty_array)
+    assert_equal [], result
+    assert_not_same empty_array, result
   end
 
   def test_find_doesnt_have_implicit_ordering