Sendevent will cause crash

Hi ,

I try to call sendevent to simulate mouse click event . I use the attachment demo on Ubuntu 16.04 + Qt 5.11. It will crash directly . I tried a lot and find some interested things.  You can check main.qml file . I put some comment on it .

1. when I use mouseArea on the outside it will crashed directly , but I try it on Qt 5.9 , the crash not happen.
2. when I delete mouseArea the crash not happen

Another thing is strange . On Qt 5.9 ,  I use two different objects as parameter to call sendevent .

One is window , it will call sendevent successfully.

Another is window's child named mainroot ,  sendevent return true but nothing happens.