Fixed stack overflow typing a date with an IME.

Same cycle the phone field fix closed: putNext() ends in setFocus(), and
on Windows a focus change with an open IME composition makes
QWindowsInputContext::reset() re-send the commit to the field we came
from, whose correctValue() fires putNext() again. Focus the next field
asynchronously, the way Ui::TimeInput already breaks this exact loop - a
re-entrancy flag would instead swallow a chained overflow digit, since
correctValue() can hand one straight on to the field after next.