add fix to avoid empty historical <think> blocks to prevent cache invalidation in long-running agentic workloads.

https://huggingface.co/Qwen/Qwen3.5-122B-A10B/discussions/22

https://www.reddit.com/r/LocalLLaMA/comments/1sg076h/i_tracked_a_major_cache_reuse_issue_down_to_qwen/

chat_template.jinja

@@ -122,7 +122,7 @@
             {%- endif %}
         {%- endif %}
         {%- set reasoning_content = reasoning_content|trim %}
-        {%- if loop.index0 > ns.last_query_index %}
+        {%- if loop.index0 > ns.last_query_index and reasoning_content %}
             {{- '<|im_start|>' + message.role + '\n<think>\n' + reasoning_content + '\n</think>\n\n' + content }}
         {%- else %}
             {{- '<|im_start|>' + message.role + '\n' + content }}