Font installer automatically creates a package to flash in case something goes wrong. Reboot the phone into recovery using Volume Up + Power button. Press the buttons until the Android logo appears, then Recovery manager should load. Use the volume buttons to navigate and power button to confirm. Select Apply Update and choose the zip file in the root directory of the internal storage. Flash it and reboot the phone. If it does not start, access the Recovery mode again, but this time use Wipe Data/Factory reset. Reboot the phone and I can guarantee it will work this way.