[BugFix] Fix an issue of modify confluent schema registry (#21552)

PR #21241 supports modifying the schema registry address, but when modifying other parameters, FE fails to pass schema registry address parameters to BE, causing the task aborted. This PR fixes the problem.

Signed-off-by: Zaorang Yang <zaorangy@gmail.com>
(cherry picked from commit c9160c9)

fe/fe-core/src/main/java/com/starrocks/analysis/RoutineLoadDataSourceProperties.java

@@ -178,7 +178,9 @@ private void checkKafkaProperties() throws AnalysisException {
         // check custom properties
         CreateRoutineLoadStmt.analyzeKafkaCustomProperties(properties, customKafkaProperties);
 
-        confluentSchemaRegistryUrl = properties.get(CreateRoutineLoadStmt.CONFLUENT_SCHEMA_REGISTRY_URL);
+        if (properties.containsKey(CreateRoutineLoadStmt.CONFLUENT_SCHEMA_REGISTRY_URL)) {
+            confluentSchemaRegistryUrl = properties.get(CreateRoutineLoadStmt.CONFLUENT_SCHEMA_REGISTRY_URL);
+        }
     }
 
     private void checkPulsarProperties() throws AnalysisException {

fe/fe-core/src/main/java/com/starrocks/load/routineload/KafkaRoutineLoadJob.java

@@ -644,7 +644,9 @@ public void modifyDataSourceProperties(RoutineLoadDataSourceProperties dataSourc
             convertCustomProperties(true);
         }
 
-        confluentSchemaRegistryUrl = dataSourceProperties.getConfluentSchemaRegistryUrl();
+        if (dataSourceProperties.getConfluentSchemaRegistryUrl() != null) {
+            confluentSchemaRegistryUrl = dataSourceProperties.getConfluentSchemaRegistryUrl();
+        }
 
         LOG.info("modify the data source properties of kafka routine load job: {}, datasource properties: {}",
                 this.id, dataSourceProperties);