Update chat_template.jinja

chat_template.jinja

@@ -3,7 +3,7 @@
     {%- set tools = custom_tools %}
 {%- endif %}
 {%- if tools is defined and tools %}
-    {%- set tool_definition = tool_definition ~ (tools | tojson(indent=4)) %}
+    {%- set tool_definition = (tool_definition|string) + ((tools | tojson(indent=4))|string) %}
 {%- else %}
     {%- set tools = none %}
 {%- endif %}