[HiCache]bug fix: fixed blank item in host_mem_release_queue (#11005)

Co-authored-by: Zuoyuan Zhang <zuoyuanzhang@ZuoyuandeMacBook-Pro.local>
Co-authored-by: Zhiqiang Xie <xiezhq@stanford.edu>

python/sglang/srt/managers/cache_controller.py

@@ -575,9 +575,11 @@ class HiCacheController:
         return operation.completed_tokens, operation.hash_value
 
     def append_host_mem_release(self, host_indices: torch.Tensor):
-        chunks = host_indices.split(self.mem_pool_host.page_size)
-        for chunk in chunks:
-            self.host_mem_release_queue.put(chunk)
+        if host_indices.numel() == 0:
+            return
+        pages = host_indices.split(self.mem_pool_host.page_size)
+        for page in pages:
+            self.host_mem_release_queue.put(page)
 
     def _page_get_zero_copy(self, operation, hash_values, host_indices):
         results = self.storage_backend.batch_get_v1(hash_values, host_indices)