type_cast_calculated_value refactor: value is never a Fixnum here. Fix test since SQLite returns Float.

[#4514 state:committed]

Signed-off-by: Jeremy Kemper <jeremy@bitsweat.net>

activerecord/lib/active_record/relation/calculations.rb

@@ -243,7 +243,7 @@ module ActiveRecord
         case operation
           when 'count' then value.to_i
           when 'sum'   then type_cast_using_column(value || '0', column)
-          when 'average' then value && (value.is_a?(Fixnum) ? value.to_f : value).to_d
+          when 'average' then value.try(:to_d)
           else type_cast_using_column(value, column)
         end
       else

activerecord/test/cases/calculations_test.rb

@@ -20,8 +20,7 @@ class CalculationsTest < ActiveRecord::TestCase
 
   def test_should_average_field
     value = Account.average(:credit_limit)
-    assert_kind_of BigDecimal, value
-    assert_equal BigDecimal.new('53.0'), value
+    assert_equal 53.0, value
   end
 
   def test_should_return_nil_as_average