add null check when import process has sub-process (#1806)

* fix bug: zk hasTask method NPE

* add retMap null check for AlertSender

* add null check when import process has sub-process

dolphinscheduler-api/src/main/java/org/apache/dolphinscheduler/api/service/ProcessDefinitionService.java

@@ -802,6 +802,8 @@ public class ProcessDefinitionService extends BaseDAGService {
                 JSONObject subParams = JSONUtils.parseObject(taskNode.getString("params"));
                 Integer subProcessId = subParams.getInteger("processDefinitionId");
                 ProcessDefinition subProcess = processDefineMapper.queryByDefineId(subProcessId);
+                //check is sub process exist in db
+                if (null != subProcess) {
                     String subProcessJson = subProcess.getProcessDefinitionJson();
                     //check current project has sub process
                     ProcessDefinition currentProjectSubProcess = processDefineMapper.queryByDefineName(targetProject.getId(), subProcess.getName());
@@ -861,7 +863,7 @@ public class ProcessDefinitionService extends BaseDAGService {
                             subParams.put("processDefinitionId", newSubProcessDefine.getId());
                             taskNode.put("params", subParams);
                         }
-
+                    }
                 }
             }
         }