update: validate_betas

Author: kozistr

pytorch_optimizer/base/optimizer.py

@@ -265,7 +265,8 @@ def validate_betas(self, betas: BETAS):
         if len(betas) < 3:
             return
 
-        self.validate_range(betas[2], 'beta3', 0.0, 1.0, range_type='[]')
+        if betas[2] is not None:
+            self.validate_range(betas[2], 'beta3', 0.0, 1.0, range_type='[]')
 
     def validate_nus(self, nus: Union[float, Tuple[float, float]]):
         if isinstance(nus, float):