Remove paste event listener on destroy

Prevent event leak from happening when hooked
event is not unhooked on destroy

Changelog: fixed

app/assets/javascripts/design_management/pages/index.vue

@@ -140,6 +140,9 @@ export default {
       this.$el.scrollIntoView();
     }
   },
+  beforeDestroy() {
+    document.removeEventListener('paste', this.onDesignPaste);
+  },
   methods: {
     resetFilesToBeSaved() {
       this.filesToBeSaved = [];

spec/frontend/design_management/pages/index_spec.js

@@ -630,6 +630,16 @@ describe('Design management index page', () => {
       expect(mockMutate).not.toHaveBeenCalled();
     });
 
+    it('does not upload designs if designs wrapper is destroyed', () => {
+      findDesignsWrapper().trigger('mouseenter');
+
+      wrapper.destroy();
+
+      document.dispatchEvent(event);
+
+      expect(mockMutate).not.toHaveBeenCalled();
+    });
+
     describe('when designs wrapper is hovered', () => {
       let realDateNow;
       const today = () => new Date('2020-12-25');