Fix analytics dropdown deselect bug

ee/app/assets/javascripts/analytics/shared/components/projects_dropdown_filter.vue

@@ -80,10 +80,13 @@ export default {
         ? this.selectedProjects.concat([selectedProject])
         : this.selectedProjects.filter(project => project.id !== selectedProject.id);
     },
+    singleSelectedProject(selectedObj, isMarking) {
+      return isMarking ? [selectedObj] : [];
+    },
     setSelectedProjects(selectedObj, isMarking) {
       this.selectedProjects = this.multiSelect
         ? this.getSelectedProjects(selectedObj, isMarking)
-        : [selectedObj];
+        : this.singleSelectedProject(selectedObj, isMarking);
     },
     onClick({ selectedObj, e, isMarking }) {
       e.preventDefault();

ee/spec/frontend/analytics/shared/components/projects_dropdown_filter_spec.js

@@ -141,6 +141,23 @@ describe('ProjectsDropdownFilter component', () => {
         ]);
       });
 
+      it('selection should be emptied when a project is deselected', () => {
+        const project = findDropdownItems().at(0);
+        project.trigger('click');
+        project.trigger('click');
+
+        expect(wrapper.emittedByOrder()).toEqual([
+          {
+            name: 'selected',
+            args: [[projects[0]]],
+          },
+          {
+            name: 'selected',
+            args: [[]],
+          },
+        ]);
+      });
+
       it('renders an avatar in the dropdown button when the project has an avatar_url', done => {
         findDropdownItems()
           .at(0)