Decrypt when downloading single events from the server

This fixes issues like not being able to view pinned messages in
encrypted rooms.

(cherry picked from commit 89e42dbc53)

# Conflicts:
#	src/libneochat/neochatroom.cpp

src/libneochat/neochatroom.cpp

@@ -1602,6 +1602,12 @@ void NeoChatRoom::downloadEventFromServer(const QString &eventId)
         }
 
         event_ptr_tt<RoomEvent> event = fromJson<event_ptr_tt<RoomEvent>>(job->jsonData());
+        if (auto encEv = eventCast<EncryptedEvent>(event.get())) {
+            auto decryptedEvent = decryptMessage(*encEv);
+            if (decryptedEvent) {
+                event = std::move(decryptedEvent);
+            }
+        }
         m_extraEvents.push_back(std::move(event));
         Q_EMIT extraEventLoaded(eventId);
     });