[Bugfix] Fix FlashInfer GDN warmup ValueError on SM90 GPUs (#36876)

vllm/model_executor/models/qwen3_next.py

@@ -137,7 +137,7 @@ def fi_chunk_gated_delta_rule(
     fi_state = initial_state.to(torch.float32)
     fi_g = g.to(torch.float32)
     fi_beta = beta.to(torch.float32)
-    output, final_state = chunk_gated_delta_rule_fi(
+    result = chunk_gated_delta_rule_fi(
         q=q,
         k=k,
         v=v,
@@ -147,8 +147,14 @@ def fi_chunk_gated_delta_rule(
         output_final_state=output_final_state,
         cu_seqlens=cu_seqlens,
     )
+    # FlashInfer returns (output, state) when output_final_state=True,
+    # or just output when output_final_state=False.
     # Unsqueeze back to 4D (1, L, H, D) to match fla output format
+    if output_final_state:
+        output, final_state = result
         return output.unsqueeze(0), final_state
+    else:
+        return result.unsqueeze(0), None
 
 
 @CustomOp.register("chunk_gated_delta_rule")