Mouse source point error caused by multi-touch

In multi-finger touch, the second touch point will not generate a touchBegin message. If you release the first finger first, and then release the second finger, it will cause m_fakeMouseSourcePointId and the current touchPoint.id() to be unequal. , This will cause the mouseRelease event to not be generated, which will cause the button to not be released.
So when there is only the last touch point left, m_fakeMouseSourcePointId should be updated.