Fix 'Image could not be created' app error on run (fix #992)
Fix 'Image could not be created' app error on run (fix #992)

Electron 9.x now crashes when passed a non-existent icon.
Also, it accepts both ico and png.
So, do our best to pass it a file that exists.

jiahaog/Nativefier,jiahaog/Nativefier,jiahaog/Nativefier