Fix polymorphic id didn't reset properly in an edge case

Refs. #3630

spec/integration/fields/polymorphic_assosiation_spec.rb

@@ -90,6 +90,30 @@
 
       is_expected.to have_selector('select#team_comment_ids')
     end
+
+    context 'with records in different models share the same id', js: true do
+      let!(:players) { [FactoryBot.create(:player, id: team.id, name: 'Jackie Robinson')] }
+
+      it 'clears the selected id on type change', js: true do
+        visit edit_path(model_name: 'comment', id: comment.id)
+        select 'Player', from: 'comment[commentable_type]'
+        click_button 'Save'
+        is_expected.to have_content 'Comment successfully updated'
+        expect(comment.reload.commentable).to eq nil
+      end
+
+      it 'updates correctly', js: true do
+        visit edit_path(model_name: 'comment', id: comment.id)
+        select 'Player', from: 'comment[commentable_type]'
+        find('input.ra-filtering-select-input').set('Rob')
+        page.execute_script("document.querySelector('input.ra-filtering-select-input').dispatchEvent(new KeyboardEvent('keydown'))")
+        expect(page).to have_selector('ul.ui-autocomplete li.ui-menu-item a')
+        page.execute_script %{[...document.querySelectorAll('ul.ui-autocomplete li.ui-menu-item')].find(e => e.innerText.includes("Jackie Robinson")).click()}
+        click_button 'Save'
+        is_expected.to have_content 'Comment successfully updated'
+        expect(comment.reload.commentable).to eq players[0]
+      end
+    end
   end
 
   context 'on show' do

src/rails_admin/filtering-select.js

@@ -297,6 +297,7 @@ import I18n from "./i18n";
     destroy: function () {
       this.input.remove();
       this.button.remove();
+      this.element.html($('<option value="" selected="selected"></option>'));
       this.element.show();
       this.filtering_select.remove();
       $.Widget.prototype.destroy.call(this);

src/rails_admin/widgets.js

@@ -258,7 +258,6 @@ import I18n from "./i18n";
             "options"
           );
           object_select.data("options", selected_data);
-          object_select.val("");
           object_select.filteringSelect("destroy");
           object_select.filteringSelect(selected_data);
         });