fix(eval): no need to check length of valid_dl when using streaming dataset (#274)

* fix(eval): StreamingDataset does not have an __len__ method.

* fix(eval): StreamingDataset has no len method

internlm/utils/evaluation.py

@@ -136,7 +136,7 @@ def evaluate_on_val_dls(
             dist.barrier()
 
             val_res = val_metric.get_metric()
-            if verbose and len(val_dl) != 0:
+            if verbose and (streaming or len(val_dl) != 0):
                 val_loss = val_loss / (val_idx + 1 + 1e-6)
                 infos = {
                     "step": step_count,