[BugFix][Qwen3-VL]: fix cu_seqlens in qwen3-vl (#11458)

python/sglang/srt/models/qwen3_vl.py

@@ -452,13 +452,15 @@ class Qwen3_VisionTransformer(nn.Module):
         position_embeddings = (emb.cos(), emb.sin())
 
         # compute cu_seqlens
+        cu_seqlens = torch.repeat_interleave(
+            grid_thw[:, 1] * grid_thw[:, 2], grid_thw[:, 0]
+        ).cumsum(dim=0)
         cu_seqlens = torch.cat(
             [
-                torch.tensor([0], device=grid_thw.device),
-                (grid_thw[:, 0] * grid_thw[:, 1] * grid_thw[:, 2]).cumsum(dim=0),
+                torch.zeros(1, dtype=torch.int32, device=cu_seqlens.device),
+                cu_seqlens.to(torch.int32),
             ]
         )
-        cu_seqlens = torch.cat([cu_seqlens.new_zeros(1), cu_seqlens])
 
         # max_seqlen, seqlens = self.compute_attn_mask_seqlen(cu_seqlens)
         x = x.unsqueeze(1)