Fix workspace parsing regex.

packages/apputils-extension/src/index.ts

@@ -241,13 +241,13 @@ const resolver: JupyterFrontEndPlugin<IWindowResolver> = {
     const { hash, path, search } = router.current;
     const query = URLExt.queryStringToObject(search || '');
     const solver = new WindowResolver();
-    const match = path.match(new RegExp(`^${paths.urls.workspaces}([^?\/]+)`));
+    const { urls } = paths;
+    const match = path.match(new RegExp(`^${urls.workspaces}\/([^?\/]+)`));
     const workspace = (match && decodeURIComponent(match[1])) || '';
     const candidate = Private.candidate(paths, workspace);
     const rest = workspace
-      ? path.replace(new RegExp(`^${paths.urls.workspaces}${workspace}`), '')
-      : path.replace(new RegExp(`^${paths.urls.app}`), '');
-
+      ? path.replace(new RegExp(`^${urls.workspaces}\/${workspace}`), '')
+      : path.replace(new RegExp(`^${urls.app}\/?`), '');
     try {
       await solver.resolve(candidate);
       return solver;