Check for empty string

src/freedombone

@@ -7548,8 +7548,10 @@ function configure_backup_key {
   apt-get -y install gnupg
   BACKUP_KEY_EXISTS=$(gpg --list-keys "$MY_NAME (backup key)")
-  if [ $BACKUP_KEY_EXISTS != *"error"* ]; then
-      return
+  if [ $BACKUP_KEY_EXISTS ]; then
+      if [ $BACKUP_KEY_EXISTS != *"error"* ]; then
+          return
+      fi
   fi
   # Generate a GPG key for backups