[dashboard] Prevent that the tab of “New Workspace“ changes when visible

Fixes gitpod-io#3764

components/dashboard/src/workspaces/StartWorkspaceModal.tsx

@@ -28,7 +28,7 @@ type Mode = 'Recent' | 'Examples' | 'Link';
 export function StartWorkspaceModal(p: StartWorkspaceModalProps) {
     const computeSelection = () => p.selected || (p.recent.length > 0 ? 'Recent' : 'Examples');
     const [selection, setSelection] = useState(computeSelection());
-    useEffect(() => setSelection(computeSelection()), [p.recent, p.selected]);
+    useEffect(() => { !p.visible && setSelection(computeSelection()) }, [p.visible, p.recent, p.selected]);
 
     const [repoUrl, setRepoUrl] = useState("");