修复撤回自定义推送bug

common/src/main/java/com/wecloud/im/ws/sender/PushTask.java

@@ -68,7 +68,8 @@ public class PushTask {
     public void push(PushModel pushModel, ImClient imClientReceiver, ImApplication imApplication) {
         log.info("push:" + imClientReceiver.getClientId());
 
-        if (pushModel != null) {
+        if (pushModel == null) {
+            pushModel = new PushModel();
             pushModel.setTitle(PUSH_TITLE);
             pushModel.setSubTitle(PUSH_BODY);
         }