support datax custom config

dolphinscheduler-api/src/test/java/org/apache/dolphinscheduler/api/utils/CheckUtilsTest.java

@@ -211,6 +211,7 @@ public class CheckUtilsTest {
         // DataxParameters
         DataxParameters dataxParameters = new DataxParameters();
         assertFalse(CheckUtils.checkTaskNodeParameters(JSONUtils.toJsonString(dataxParameters), TaskType.DATAX.toString()));
+        dataxParameters.setCustomConfig(0);
         dataxParameters.setDataSource(111);
         dataxParameters.setDataTarget(333);
         dataxParameters.setSql("sql");

dolphinscheduler-common/src/main/java/org/apache/dolphinscheduler/common/task/datax/DataxParameters.java

@@ -186,6 +186,7 @@ public class DataxParameters extends AbstractParameters {
 
     @Override
     public boolean checkParameters() {
+        if (customConfig == null) return false;
         if (customConfig == 0) {
             return dataSource != 0
                     && dataTarget != 0