Update chat_template.jinja

chat_template.jinja

@@ -205,7 +205,7 @@
         {%- set reasoning_effort = "medium" %}
     {%- endif %}
     {{- "Reasoning: " + reasoning_effort + "\n\n" }}
-    {%- if builtin_tools %}
+    {%- if builtin_tools is defined and builtin_tools is not none %}
         {{- "# Tools\n\n" }}
         {%- set available_builtin_tools = namespace(browser=false, python=false) %}
         {%- for tool in builtin_tools %}