text: Title: Fix: Error using enforce_privacy = True
  Body: https://github.com/gventuri/pandas-ai/blob/87dd966e52c21e6359f2797f80826cd49c6bd40f/pandasai/smart_dataframe/__init__.py#L436C57-L436C57
  
  When using `enforce_privacy = True`
  generates an error because it only sends the headers and when using `_truncate_head_columns` it tries to truncate 0 rows
  
  so I propose the following:
  
  ```python
           if self.lake.config.enforce_privacy:
              return sampled_head
          else:
              return self._truncate_head_columns(sampled_head)
  ```
  Instead of using:
  
  ```python
           return self._truncate_head_columns(sampled_head)
  ```
  This avoids the errors reported by users who use `enforce_privacy = True`