for difficult voc xml

paddlex/cv/datasets/voc.py

@@ -128,7 +128,10 @@ class VOCDetection(Dataset):
                     gt_class[i][0] = cname2cid[cname]
                     pattern = re.compile('<difficult>', re.IGNORECASE)
                     diff_tag = pattern.findall(str(ET.tostringlist(obj)))[0][1:-1]
-                    _difficult = int(obj.find(diff_tag).text)
+                    try:
+                        _difficult = int(obj.find(diff_tag).text)
+                    except Exception:
+                        _difficult = 0
                     pattern = re.compile('<bndbox>', re.IGNORECASE)
                     box_tag = pattern.findall(str(ET.tostringlist(obj)))[0][1:-1]
                     box_element = obj.find(box_tag)