fix: user page not found (#3736)

#### What type of PR is this?
/kind bug
/area core

#### What this PR does / why we need it:
修复作者页无法访问的问题

#### Which issue(s) this PR fixes:
Fixes #3718

#### Does this PR introduce a user-facing change?
```release-note
修复作者页无法访问的问题
```

application/src/main/java/run/halo/app/theme/router/ThemeCompositeRouterFunction.java

@@ -127,6 +127,7 @@ public class ThemeCompositeRouterFunction implements RouterFunction<ServerRespon
 
         // Add the index route to the end to prevent conflict with the queryParam rule of the post
         routePatterns.add(new RoutePattern(DefaultTemplateEnum.INDEX, "/"));
+        routePatterns.add(new RoutePattern(DefaultTemplateEnum.AUTHOR, ""));
         return routePatterns;
     }
 }

application/src/main/java/run/halo/app/theme/router/factories/AuthorPostsRouteFactory.java

@@ -18,6 +18,7 @@ import run.halo.app.core.extension.User;
 import run.halo.app.extension.ReactiveExtensionClient;
 import run.halo.app.infra.SystemConfigurableEnvironmentFetcher;
 import run.halo.app.infra.SystemSetting;
+import run.halo.app.infra.exception.NotFoundException;
 import run.halo.app.theme.DefaultTemplateEnum;
 import run.halo.app.theme.finders.PostFinder;
 import run.halo.app.theme.finders.vo.ListedPostVo;
@@ -73,7 +74,8 @@ public class AuthorPostsRouteFactory implements RouteFactory {
     }
 
     private Mono<UserVo> getByName(String name) {
-        return client.get(User.class, name)
+        return client.fetch(User.class, name)
+            .switchIfEmpty(Mono.error(() -> new NotFoundException("Author page not found.")))
             .map(UserVo::from);
     }
 }

application/src/test/java/run/halo/app/theme/router/factories/AuthorPostsRouteFactoryTest.java

@@ -33,7 +33,7 @@ class AuthorPostsRouteFactoryTest extends RouteFactoryTestSuite {
         RouterFunction<ServerResponse> routerFunction = authorPostsRouteFactory.create(null);
         WebTestClient webClient = getWebTestClient(routerFunction);
 
-        when(client.get(eq(User.class), eq("fake-user")))
+        when(client.fetch(eq(User.class), eq("fake-user")))
             .thenReturn(Mono.just(new User()));
         webClient.get()
             .uri("/authors/fake-user")