fix: 修复了在else语句中调用'schema_str'之前未定义的问题 (#1719)

重新排列了方法中的条件返回语句，以确保在使用之前始终定义了'schema_str'。

crazy_functions/json_fns/pydantic_io.py

@@ -62,8 +62,8 @@ class GptJsonIO():
         if "type" in reduced_schema:
             del reduced_schema["type"]
         # Ensure json in context is well-formed with double quotes.
-        if self.example_instruction:
         schema_str = json.dumps(reduced_schema)
+        if self.example_instruction:
             return PYDANTIC_FORMAT_INSTRUCTIONS.format(schema=schema_str)
         else:
             return PYDANTIC_FORMAT_INSTRUCTIONS_SIMPLE.format(schema=schema_str)