This problem is still happening with 4.3.10 on Windows-10 Pro (OS-build 19043.1706). If I open the application and create a file and save it off, all is fine but if I open an existing PNG file and store it elsewhere (say the desktop) with a different name, the phantom 0-byte .pdnSave file is created.
Let me know if any debug info is needed or if you need me to share any further details.