fix(ui): failing test cases for form manip utils

Author: psychedelicious

invokeai/frontend/web/src/features/nodes/components/sidePanel/builder/form-manipulation.test.ts

@@ -80,7 +80,7 @@ describe('workflow builder form manipulation', () => {
         index: 0,
       });
 
-      expect(getElement(form, el.id, isContainerElement).parentId).toBe(form.rootElementId);
+      expect(getElement(form, el.id).parentId).toBe(form.rootElementId);
     });
 
     it('should add the element at the given index', () => {

invokeai/frontend/web/src/features/nodes/components/sidePanel/builder/form-manipulation.ts

@@ -125,6 +125,11 @@ export const addElement = (args: {
   const { form, element, parentId, index } = args;
   const { elements } = form;
 
+  if (element.id in elements) {
+    // Element already exists
+    return false;
+  }
+
   const parent = elements[parentId];
   if (!parent || !isContainerElement(parent)) {
     return false;