fix bug

@@ -36,7 +36,7 @@ class Comparison:
 
 
     def common_compare(self, input_str, ocr_str, idx, **kwargs):
     def common_compare(self, input_str, ocr_str, idx, **kwargs):
         if not isinstance(input_str, str) or not isinstance(ocr_str, str):
         if not isinstance(input_str, str) or not isinstance(ocr_str, str):
-            return self.RESULT_N
+            return self.RESULT_N, ocr_str
         return self.build_res(input_str == ocr_str), ocr_str
         return self.build_res(input_str == ocr_str), ocr_str
 
 
     def name_compare(self, input_str, ocr_str, idx, **kwargs):
     def name_compare(self, input_str, ocr_str, idx, **kwargs):