check for none in epoch best

mlair/run_modules/training.py

@@ -166,6 +166,7 @@ class Training(RunEnvironment):
                                workers=psutil.cpu_count(logical=False))
             history = hist
         epoch_best = checkpoint.epoch_best
+        if epoch_best is not None:
             logging.info(f"best epoch: {epoch_best + 1}")
         try:
             lr = self.callbacks.get_callback_by_name("lr")