While updating Notepad++, the updater window showed no title or information. Is this okay from security point of view ?
This is perfectly fine.
When a program opens a window, it sends to it a few parameters including the window title, main text, button labels, etc. In this case, it seems like the updater simply hasn't given any such information. It's silly from a UI point of view, but there are no security implications with this behavior.
Your software offers a GPG signature so that you can verify you did not download a malware.
You can also check your HTTP requests while updating.