Check for empty string

src/freedombone

@@ -7556,6 +7556,9 @@ function configure_backup_key {
 
   # Generate a GPG key for backups
   BACKUP_KEY_EXISTS=$(su -c "gpg --list-keys \"$MY_NAME (backup key)\"" - $MY_USERNAME)
+  if [ ! $BACKUP_KEY_EXISTS ]; then
+      BACKUP_KEY_EXISTS='error'
+  fi
   if [ $BACKUP_KEY_EXISTS == *"error"* ]; then
       echo 'Key-Type: 1' > /home/$MY_USERNAME/gpg-genkey.conf
       echo 'Key-Length: 4096' >> /home/$MY_USERNAME/gpg-genkey.conf