fix npe

Author: shedfreez

polaris-common/polaris-model/src/main/java/com/tencent/polaris/api/utils/ApiTrieUtil.java

@@ -127,7 +127,7 @@ public static TrieNode<String> buildConfigTrieNode(String prefix, TrieNode<Strin
     }
 
     public static boolean checkConfig(TrieNode<String> root, String config) {
-        if (root == null || root.isEmptyChildren()) {
+        if (root == null || root.isEmptyChildren() || StringUtils.isEmpty(config)) {
             return false;
         }
 

polaris-common/polaris-model/src/test/java/com/tencent/polaris/api/utils/ApiTrieUtilTest.java

@@ -52,6 +52,7 @@ public void testCheckConfig() {
         assertThat(ApiTrieUtil.checkConfig(root1, "provider")).isFalse();
         assertThat(ApiTrieUtil.checkConfig(root1, "provider.config")).isTrue();
         assertThat(ApiTrieUtil.checkConfig(root1, "provider.config.nameList[1]")).isTrue();
+        assertThat(ApiTrieUtil.checkConfig(root1, null)).isFalse();
 
         TrieNode<String> root2 = ApiTrieUtil.buildConfigTrieNode("provider.conf");
         assertThat(ApiTrieUtil.checkConfig(root2, "provider.conf.test")).isTrue();