fix non-integer relation

Author: olegantonyan

lib/polymorphic_integer_type/activerecord_5_0_0/polymorphic_array_value_extension.rb

@@ -29,7 +29,7 @@ def type_to_ids_mapping
 
           hash[key] << convert_to_id(value)
         else
-          hash[klass.polymorphic_name] << convert_to_id(value)
+          hash[klass(value)&.polymorphic_name] << convert_to_id(value)
         end
       end
     end