Firefox Portable Nightly (64.0 Alpha 1) installer silently fails

Steps to reproduce:

• Run Firefox Nightly installation
  (either from PA updater or installer from site will do)
• wait until it successfully finish
• try running the app

Result:

• Error message "Mozilla Firefox, Portable Edition cannot be started. You may wish to re-install to fix this issue. (ERROR: firefox.exe could not be found)"

Expected:

• Firefox Nightly portable starts

Workaround:

• Rename "App/core" folder to "App/Firefox" manually

OS:

• Windows 10 (1803) x64