[civiremote_entity] Rebuild form in case of error

Previously on error a redirect to the destination (URL parameter) was
executed, if given. Otherwise, a redirect to the form page was executed.
Now in both cases the form is rebuild (so the entered values are kept).

modules/civiremote_entity/src/Form/AbstractEntityForm.php

@@ -119,6 +119,7 @@ public function submitForm(array &$form, FormStateInterface $formState): void {
     }
     catch (ApiCallFailedException $e) {
       $this->messenger()->addError($this->t('Submitting form failed: @error', ['@error' => $e->getMessage()]));
+      $formState->setRebuild(TRUE);
 
       return;
     }