helper erro handling

lib/parfait/space.rb

@@ -115,7 +115,9 @@ module Parfait
 
     # get the current instance_typ of the class with the given name
     def get_type_by_class_name(name)
-      get_class_by_name(name).instance_type
+      clazz = get_class_by_name(name)
+      return nil unless clazz
+      clazz.instance_type
     end
 
     # get a class by name (symbol)

test/parfait/test_space.rb

@@ -28,6 +28,9 @@ module Parfait
     def test_get_type_by_class_name
       assert_equal Parfait::Type , Parfait.object_space.get_type_by_class_name(:Space).class
     end
+    def test_get_type_by_class_name_nil
+      assert_nil Parfait.object_space.get_type_by_class_name(:Spac)
+    end
     def test_get_integer_instance
       int = @space.get_integer
       assert_equal Integer , int.class