FIX: Empty param-inout form should reject submit (#309)

The `onSubmit` hook will only be triggered when the form is valid, so we
need to clear the contents of `serializedData` in advance in `submit`.
Otherwise, it may not throw a validation error.

assets/javascripts/discourse/components/param-input-form.gjs

@@ -278,6 +278,7 @@ export default class ParamInputForm extends Component {
     if (this.form == null) {
       throw "No form";
     }
+    this.serializedData = null;
     await this.form.submit();
     if (this.serializedData == null) {
       throw new ParamValidationError("validation_failed");
@@ -293,7 +294,6 @@ export default class ParamInputForm extends Component {
 
   @action
   onSubmit(data) {
-    this.serializedData = null;
     const serializedData = {};
     for (const [id, val] of Object.entries(data)) {
       serializedData[id] =

assets/javascripts/discourse/controllers/group-reports-show.js

@@ -91,7 +91,7 @@ export default class GroupReportsShowController extends Controller {
     } catch (error) {
       if (error.jqXHR?.status === 422 && error.jqXHR.responseJSON) {
         this.results = error.jqXHR.responseJSON;
-      } else if (error instanceof ParamValidationError) {
+      } else if (!(error instanceof ParamValidationError)) {
         popupAjaxError(error);
       }
     } finally {