Added fallback for empty error messages.

In the case where the data.errors object does not have any explicit errors, the diff adds a fallback. The resulting error message displayed will then be the general data message. This prevents situations where the user receives an empty error message.

exmplate/script.js

@@ -159,6 +159,9 @@
                 for (let key in data.errors) {
                     errorMessage += data.errors[key] + '<br>';
                 }
+                if (errorMessage === '') {
+                    errorMessage = data.message;
+                }
                 setError(errorMessage, button);
                 return
             }