Handle case where object doesn't support inspect

Author: johnnyshields

lib/mongoid/errors/invalid_field_type_definition.rb

@@ -15,9 +15,11 @@ class InvalidFieldTypeDefinition < MongoidError
       # @param [ Object ] field_type The object which is expected to a be Symbol or String.
       # @param [ Object ] klass The object which is expected to be a Class or Module.
       def initialize(field_type, klass)
+        type_inspection = field_type.try(:inspect) || field_type.class.inspect
+        klass_inspection = klass.try(:inspect) || klass.class.inspect
         super(
           compose_message('invalid_field_type_definition',
-            type_inspection: field_type.inspect, klass_inspection: klass.inspect)
+            type_inspection: type_inspection, klass_inspection: klass_inspection)
         )
       end
     end