[Minor] Add some utility functions (#1671)

python/sglang/srt/managers/scheduler.py

@@ -710,7 +710,7 @@ class Scheduler:
                     next_token_ids
                 )
 
-            if logits_output:
+            if batch.return_logprob:
                 # Move logprobs to cpu
                 if logits_output.next_token_logprobs is not None:
                     logits_output.next_token_logprobs = (
@@ -786,7 +786,7 @@ class Scheduler:
         self.num_generated_tokens += len(batch.reqs)
 
         # Move logprobs to cpu
-        if logits_output.next_token_logprobs is not None:
+        if batch.return_logprob:
             next_token_logprobs = logits_output.next_token_logprobs[
                 torch.arange(len(next_token_ids), device=next_token_ids.device),
                 next_token_ids,