[Browse] Handle missing path and nav to root

When no path is specified, don't throw error.  Navigate
to default, as expected.

When navigating to root, navigate to the last child
of root instead.  This handles cases where DEFAULT_PATH
is not found (e.g. deployments without "mine").

platform/commonUI/browse/src/BrowseController.js

@@ -113,11 +113,22 @@ define(
                 $location.path('/browse/' + currentIds);
             }
 
+            function getLastChildIfRoot(object) {
+                if (object.getId() !== 'ROOT') {
+                    return object;
+                }
+                return object.useCapability('composition')
+                    .then(function (composees) {
+                        return composees[composees.length - 1];
+                    });
+            }
+
             function navigateToPath(path) {
                 return getObject('ROOT')
                     .then(function (root) {
                         return findViaComposition(root, path);
                     })
+                    .then(getLastChildIfRoot)
                     .then(function (object) {
                         navigationService.setNavigation(object);
                     });
@@ -147,10 +158,14 @@ define(
             // navigate to the path ourselves, which results in it being
             // properly set.
             $scope.$on('$routeChangeStart', function (event, route) {
-                if (route.$$route === $route.current.$$route &&
+                if (route.$$route === $route.current.$$route) {
+                    if (route.pathParams.ids &&
                         route.pathParams.ids !== $route.current.pathParams.ids) {
                         event.preventDefault();
                         navigateToPath(route.pathParams.ids.split('/'));
+                    } else {
+                        navigateToPath([]);
+                    }
                 }
             });