修复GradientClip在update_every的场景下会更新错误的问题

fastNLP/core/callback.py

@@ -399,10 +399,11 @@ class GradientClipCallback(Callback):
         self.clip_value = clip_value
     
     def on_backward_end(self):
-        if self.parameters is None:
-            self.clip_fun(self.model.parameters(), self.clip_value)
-        else:
-            self.clip_fun(self.parameters, self.clip_value)
+        if self.step%self.update_every==0:
+            if self.parameters is None:
+                self.clip_fun(self.model.parameters(), self.clip_value)
+            else:
+                self.clip_fun(self.parameters, self.clip_value)
 
 
 class EarlyStopCallback(Callback):