Suppress scalar warnings (#10509)

tools/program.py

@@ -346,7 +346,10 @@ def train(config,
                 lr_scheduler.step()
 
             # logger and visualdl
-            stats = {k: v.numpy().mean() for k, v in loss.items()}
+            stats = {
+                k: float(v) if v.shape == [] else v.numpy().mean()
+                for k, v in loss.items()
+            }
             stats['lr'] = lr
             train_stats.update(stats)