[BugFix] Fix NPE in HeartbeatMgr when FE node is not available (StarR…

…ocks#54997)

Fixes 
```
Cannot invoke "com.starrocks.http.rest.BootstrapFinishAction$BootstrapResult.getStatus()" because "result" is null
```

Signed-off-by: gengjun-git <[email protected]>

fe/fe-core/src/main/java/com/starrocks/common/util/Util.java

@@ -356,7 +356,7 @@ public static boolean checkColumnSupported(List<Column> columns) {
     //      Base64.encodeBase64String("user:passwd".getBytes());
     // If no auth info, pass a null.
     public static String getResultForUrl(String urlStr, String encodedAuthInfo, int connectTimeoutMs,
-                                         int readTimeoutMs) {
+                                         int readTimeoutMs) throws Exception {
         StringBuilder sb = new StringBuilder();
         InputStream stream = null;
         String safeUrl = urlStr;
@@ -379,7 +379,7 @@ public static String getResultForUrl(String urlStr, String encodedAuthInfo, int
             }
         } catch (Exception e) {
             LOG.warn("failed to get result from url: {}. {}", safeUrl, e.getMessage());
-            return null;
+            throw e;
         } finally {
             if (stream != null) {
                 try {

fe/fe-core/src/test/java/com/starrocks/common/util/UtilTest.java

@@ -0,0 +1,27 @@
+// Copyright 2021-present StarRocks, Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.starrocks.common.util;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class UtilTest {
+
+    @Test
+    public void testGetResultForUrl() {
+        Assert.assertThrows(Exception.class,
+                () -> Util.getResultForUrl("http://127.0.0.1:23/invalid", null, 1000, 1000));
+    }
+}