也许没有帮助前任作者，但其他人却遇到了问题。
我只是错误地将一个调试库与一个发行版一起使用而得到了这个错误。因此，如果确定执行正确（首先实例化应用程序，然后使用小部件），请检查链接器设置。

Maybe not helping the former author, but others facing the problem. I simply got this error by mistaking a debug-library with a release one. So check your linker settings, if you are sure the implementation is done right (first instancing application and then using widgets).