Fix find_msg by enusring ai_res always return str or None

[PiotrCzapla]

If I understand correctly, prompt now looks like this;

res = {
    'output_type': 'display_data',
    'metadata': {'is_ai_res': True},
    'data': {
        'text/markdown': ['Line 1\n', 'Line 2']
    }
}

Then nested_idx(res, 'data', 'text/markdown') returns a list: ['Line 1\n', 'Line 2']
that needs joining. Using: join_out as it accept also moments where nested_idx returns a string.

Here is the error:

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Cell In[27], line 1
----> 1 await sync_updates('mini-updates')

Cell In[24], line 4, in sync_updates(ch, dname, limit)
      1 async def sync_updates(ch, dname='', limit=500):
      2     "Add new Discord msgs from channel `ch` (name, url, or obj) into the dialog"
      3     ch = await to_channel(ch)
----> 4     synced = await find_msgs(r':::\{#sf(\d+)', dname=dname)
      5     synced_by_id = {sfid: msg for msg in synced
      6                     for sfid in re.findall(r':::\{#sf(\d+)', msg['content'])}
      7     msgs, before = [], None

File ~/aai-ws/fastaudit/fastaudit/core.py:64, in CallTracker.wrap.<locals>._fn(*args, **kwargs)
     62 @wraps(fn)
     63 async def _fn(*args, **kwargs):
---> 64     with self.track(fn, args, kwargs): return await fn(*args, **kwargs)

File ~/aai-ws/dialoghelper/dialoghelper/core.py:543, in find_msgs(re_pattern, msg_type, before, after, context, use_case, use_regex, only_err, only_exp, ids, limit, include_output, include_meta, as_xml, nums, trunc_out, trunc_in, headers_only, header_section, include_skipped, dname)
    541 d = _cells2dlg(await cells_client(dname).cells(), name=find_dname(dname, required=False) or '-')
    542 ms = [m for m in d.messages if include_skipped or not m.skipped]
--> 543 found = Dialog(ms).find_msgs(re_pattern, msg_type=msg_type, only_err=only_err, only_exp=only_exp, ids=ids, limit=limit,
    544     use_case=use_case, use_regex=use_regex, headers_only=headers_only, header_section=header_section,
    545     before=max(before, context), after=max(after, context), context=0)
    546 def _d(m):
    547     o = m.todict()

File ~/aai-ws/aidialog/aidialog/dlgskill.py:218, in find_msgs(self, re_pattern, msg_type, only_err, only_exp, ids, before, after, context, limit, use_case, use_regex, headers_only, header_section, pred)
    216     if idset is not None and m.id not in idset: return False
    217     return not pat or bool(pat.search(_txt(m)))
--> 218 hits = [i for i,m in enumerate(ms) if _ok(m)]
    219 if limit is not None: hits = hits[:limit]
    220 matched = {ms[i].id for i in hits}

File ~/aai-ws/aidialog/aidialog/dlgskill.py:217, in find_msgs.<locals>._ok(m)
    215 if pred and not pred(m): return False
    216 if idset is not None and m.id not in idset: return False
--> 217 return not pat or bool(pat.search(_txt(m)))

File ~/aai-ws/aidialog/aidialog/dlgskill.py:209, in find_msgs.<locals>._txt(m)
--> 209 def _txt(m): return m.content + ('\n'+m.ai_res if m.msg_type==sprompt and m.ai_res else '')

TypeError: can only concatenate str (not "list") to str