Fix potential threading issue.

state.go

@@ -259,8 +259,6 @@ func (s *State) ChannelRemove(channel *Channel) error {
 	if err != nil {
 		return err
 	}
-	
-	delete(s.channelMap, channel.ID)
 
 	if channel.IsPrivate {
 		s.Lock()
@@ -269,7 +267,7 @@ func (s *State) ChannelRemove(channel *Channel) error {
 		for i, c := range s.PrivateChannels {
 			if c.ID == channel.ID {
 				s.PrivateChannels = append(s.PrivateChannels[:i], s.PrivateChannels[i+1:]...)
-				return nil
+				break
 			}
 		}
 	} else {
@@ -284,10 +282,12 @@ func (s *State) ChannelRemove(channel *Channel) error {
 		for i, c := range guild.Channels {
 			if c.ID == channel.ID {
 				guild.Channels = append(guild.Channels[:i], guild.Channels[i+1:]...)
-				return nil
+				break
 			}
 		}
 	}
+	
+	delete(s.channelMap, channel.ID)
 
 	return nil
 }