Don't log chat as it makes status-desktop blow up

For some reason when calling saveChat from desktop with `lastMessage`
set to null, a sigsev is received.
The issue seems to be in logFormat
05280a7ae3/log/format.go (L356)
which for some reason blows up if passed a nil pointer (`lastMessage`).
Can't replicate on any other platform or running it locally, but hey,
this fixes the issue.

VERSION

@@ -1 +1 @@
-0.57.1
+0.57.2

services/ext/api.go

@@ -238,7 +238,6 @@ func (api *PublicAPI) LoadFilters(parent context.Context, chats []*transport.Fil
 }
 
 func (api *PublicAPI) SaveChat(parent context.Context, chat *protocol.Chat) error {
-	api.log.Info("saving chat", "chat", chat)
 	return api.service.messenger.SaveChat(chat)
 }