fix ppdet/utils/states (#8421)

* fix a code

* fix the tensor to float

ppdet/utils/stats.py

@@ -74,7 +74,7 @@ class TrainingStats(object):
                 for k in stats.keys()
             }
         for k, v in self.meters.items():
-            v.update(stats[k].numpy())
+            v.update(float(stats[k]))
 
     def get(self, extras=None):
         stats = collections.OrderedDict()