Simplify message search channel resolution logic

discord/abc.py

@@ -319,13 +319,14 @@ async def _handle_message_search(
     if offset < 0:
         raise ValueError('offset must be greater than or equal to 0')
 
+    _channels = {c.id: c for c in channels} if channels else {}
+
     # Guild channels must go through the guild search endpoint
     _state = destination._state
     endpoint = _state.http.search_guild
-    entity_id = None
-    channel = None
     if isinstance(destination, Messageable):
         channel = await destination._get_channel()
+        _channels[channel.id] = channel
         if isinstance(channel, PrivateChannel):
             endpoint = _state.http.search_channel
             entity_id = channel.id
@@ -334,13 +335,10 @@ async def _handle_message_search(
             entity_id = getattr(channel.guild, 'id', getattr(channel, 'guild_id', None))
     else:
         entity_id = destination.id
+
     if not entity_id:
         raise ValueError('Could not resolve channel guild ID')
 
-    _channels = {c.id: c for c in channels} if channels else {}
-    if channel:
-        _channels[channel.id] = channel
-
     def _resolve_channel(message: PartialMessagePayload, /):
         _channel, _ = _state._get_guild_channel(message)
         if isinstance(_channel, PartialMessageable) and _channel.id in _channels:

discord/message.py

@@ -691,7 +691,7 @@ class PartialMessage(Hashable):
         self.guild: Optional[Guild] = getattr(channel, 'guild', None)
         self.guild_id: Optional[int] = self.guild.id if self.guild else None
         if hasattr(channel, 'guild_id'):
-            if self.guild_id:
+            if self.guild_id is not None:
                 channel.guild_id = self.guild_id  # type: ignore
             else:
                 self.guild_id = channel.guild_id  # type: ignore