fix: there may not be weight ratio in multilabel dataset label (#3227)

ppcls/loss/multilabelloss.py

@@ -39,7 +39,7 @@ def _labelsmoothing(self, target, class_num):
     def _binary_crossentropy(self, input, target, class_num):
         if self.weight_ratio:
             target, label_ratio = target[:, 0, :], target[:, 1, :]
-        else:
+        elif target.ndim == 3:
             target = target[:, 0, :]
         if self.epsilon is not None:
             target = self._labelsmoothing(target, class_num)