fix issues like null point check.

Signed-off-by: boxwall <hezhiqiang19@huawei.com>
Change-Id: Ieac2de6ea8883887c6373ffcfba4a5fe03f420a2

frameworks/event_handler.cpp

@@ -42,6 +42,9 @@ bool EventHandler::IsRunning()
 
 void EventHandler::EventDispatch(EventHandler *hdl)
 {
+    if (hdl == nullptr) {
+        return;
+    }
     std::unique_lock<std::mutex> lock(hdl->mtx_);
     hdl->running_ = true;
     while (hdl->running_) {