Hide rollup weight when null

What does this MR do and why?

Hide rollup weight when zero

Changelog: changed

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

There is no use case to validate the null rolledUpWeight right now with rollUp set to true in work item weight widget. We can confirm the behavior by applying the following patch

diff --git a/app/assets/javascripts/work_items/components/work_item_detail.vue b/app/assets/javascripts/work_items/components/work_item_detail.vue
index d1d568df835a..1ca411d84082 100644
--- a/app/assets/javascripts/work_items/components/work_item_detail.vue
+++ b/app/assets/javascripts/work_items/components/work_item_detail.vue
@@ -286,7 +286,7 @@ export default {
       return this.workItemWeight?.widgetDefinition?.rollUp;
     },
     rolledUpWeight() {
-      return this.workItemWeight?.rolledUpWeight;
+      return null;
     },
     workItemBodyClass() {
       return {

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Go to epic work item and apply the above patch
2. See that if the rollup weight is null it would be hidden