Fix sidebar labels scoped label selection bug

When a scoped label is currently selected in the label dropdown,
then if another scoped label from the same set is picked then
the currently selected scoped label is sometimes not unselected.

app/assets/javascripts/vue_shared/components/sidebar/labels_select_vue/store/mutations.js

@@ -69,7 +69,8 @@ export default {
     if (isScopedLabel(candidateLabel)) {
       const scopedKeyWithDelimiter = `${scopedLabelKey(candidateLabel)}${SCOPED_LABEL_DELIMITER}`;
       const currentActiveScopedLabel = state.labels.find(
-        ({ title }) => title.startsWith(scopedKeyWithDelimiter) && title !== candidateLabel.title,
+        ({ set, title }) =>
+          set && title.startsWith(scopedKeyWithDelimiter) && title !== candidateLabel.title,
       );
 
       if (currentActiveScopedLabel) {

spec/frontend/vue_shared/components/sidebar/labels_select_vue/store/mutations_spec.js

@@ -159,8 +159,9 @@ describe('LabelsSelect Mutations', () => {
       labels = [
         { id: 1, title: 'scoped' },
         { id: 2, title: 'scoped::one', set: false },
-        { id: 3, title: 'scoped::test', set: true },
-        { id: 4, title: '' },
+        { id: 3, title: 'scoped::two', set: false },
+        { id: 4, title: 'scoped::three', set: true },
+        { id: 5, title: '' },
       ];
     });
 
@@ -191,8 +192,9 @@ describe('LabelsSelect Mutations', () => {
         expect(state.labels).toEqual([
           { id: 1, title: 'scoped' },
           { id: 2, title: 'scoped::one', set: true, touched: true },
-          { id: 3, title: 'scoped::test', set: false },
-          { id: 4, title: '' },
+          { id: 3, title: 'scoped::two', set: false },
+          { id: 4, title: 'scoped::three', set: false },
+          { id: 5, title: '' },
         ]);
       });
     });