BugFix(hicache): Fix host indices out of bound error (#9637)

Co-authored-by: Zhiqiang Xie <xiezhq@stanford.edu>

python/sglang/srt/managers/cache_controller.py

@@ -616,12 +616,13 @@ class HiCacheController:
                     f"Prefetch operation {operation.request_id} failed to retrieve page {hash_values[i]}."
                 )
                 break
-            self.mem_pool_host.set_from_flat_data_page(
-                host_indices[operation.completed_tokens],
-                page_data[i],
-            )
-            if not operation.increment(self.page_size):
-                break  # Operation terminated by controller
+            if operation.increment(self.page_size):
+                self.mem_pool_host.set_from_flat_data_page(
+                    host_indices[i * self.page_size],
+                    page_data[i],
+                )
+            else:
+                break
 
     def _page_transfer(self, operation):
         # Select the get function and batch size