A crash occurs if updateItemStates runs between the

UpdateItemStatesThread finishing and the finished() signal being
delivered.

In this case, a new thread was not created, because the old thread
still existed. However, pendingItemStatesUpdate was not set, because the
thread was not running. Instead, the old thread was restarted.

This meant that the finished() signal from the first run could be delivered
while the thread was running for a second time, causing the thread to be
deleted while still running and thus a crash.

Solution: set pendingItemStatesUpdate if the thread is non-null,
even if it is not running, knowing that slotThreadFinished has not yet run,
and will call updateItemStates itself.

BUG: 302264
FIXED-IN: 4.10
REVIEW: 107656