Check for backup key file

src/freedombone-utils-keys

             cp -r $USB_MOUNT/letsencrypt/* /etc/letsencrypt
         fi
 
-        if [ -f $USB_MOUNT/.mastergpgkey && -f $USB_MOUNT/.backupgpgkey ]; then
+        if [ -f $USB_MOUNT/.mastergpgkey ]; then
             # Recovering keys from file rather than just copying the gnupg
             # directory may help to avoid problems during upgrades/reinstalls
+            if [ ! -f $USB_MOUNT/.backupgpgkey ]; then
+                echo $'No backup key file found on USB drive'
+                exit 725729
+            fi
             gpg --homedir=/home/$MY_USERNAME/.gnupg --allow-secret-key-import --import $USB_MOUNT/.mastergpgkey
             echo "$BACKUP_DUMMY_PASSWORD" | gpg --batch --passphrase-fd 0 --homedir=/home/$MY_USERNAME/.gnupg --allow-secret-key-import --import $USB_MOUNT/.backupgpgkey
             if [ -d /home/$MY_USERNAME/.gnupg ]; then