fix to set placeholder images in chat

Signed-off-by: Marcel Hibbe <dev@mhibbe.de>

app/src/main/java/com/nextcloud/talk/controllers/ChatController.kt

@@ -621,8 +621,8 @@ class ChatController(args: Bundle) :
             adapter = TalkMessagesListAdapter(
                 senderId,
                 messageHolders,
-                ImageLoader { imageView, url, _ ->
-                    imageView.loadAvatarOrImagePreview(url!!, conversationUser, placeholder = payload as? Drawable)
+                ImageLoader { imageView, url, placeholder ->
+                    imageView.loadAvatarOrImagePreview(url!!, conversationUser, placeholder as Drawable?)
                 },
                 this
             )