[fix][broker] Fix NPE when updating topic's properties (apache#17352)

Co-authored-by: bjhuxiaohua <[email protected]>
(cherry picked from commit f1d1158)

pulsar-broker/src/test/java/org/apache/pulsar/broker/admin/AdminApi2Test.java

@@ -909,11 +909,14 @@ public void testUpdatePartitionedTopicProperties() throws Exception {
         final String topicNameTwo = "persistent://" + namespace + "/testUpdatePartitionedTopicProperties2";
         admin.namespaces().createNamespace(namespace, 20);
 
-        // create partitioned topic with properties
+        // create partitioned topic without properties
+        admin.topics().createPartitionedTopic(topicName, 2);
+        Map<String, String> properties = admin.topics().getProperties(topicName);
+        Assert.assertNull(properties);
         Map<String, String> topicProperties = new HashMap<>();
         topicProperties.put("key1", "value1");
-        admin.topics().createPartitionedTopic(topicName, 2, topicProperties);
-        Map<String, String> properties = admin.topics().getProperties(topicName);
+        admin.topics().updateProperties(topicName, topicProperties);
+        properties = admin.topics().getProperties(topicName);
         Assert.assertNotNull(properties);
         Assert.assertEquals(properties.get("key1"), "value1");