[Structured Outputs] [Bug] Fix misalignment in apply_grammar_bitmask causing...

[Structured Outputs] [Bug] Fix misalignment in apply_grammar_bitmask causing unintended masking and NaN logits (#22963)
Signed-off-by: rishitdholakia13 <rishit+github@cohere.com>

vllm/v1/worker/gpu_model_runner.py

@@ -1355,10 +1355,10 @@ class GPUModelRunner(LoRAModelRunnerMixin, KVConnectorModelRunnerMixin):
             cumulative_index += 1 + num_spec_tokens
         grammar_bitmask = sorted_bitmask
 
-        # If the grammar bitmask and the logits have the same shape
+        # If the length of out indices and the logits have the same shape
         # we don't need to pass indices to the kernel,
         # since the bitmask is already aligned with the logits.
-        skip_out_indices = grammar_bitmask.shape[0] == logits.shape[0]
+        skip_out_indices = len(out_indices) == logits.shape[0]
 
         # Serialization of np.ndarray is much more efficient than a tensor,
         # so we receive it in that format.