Fix AbstractClient::adjustedSize() for wayland windows with no committed buffer
AbstractClient::constrainClientSize() forces the minimum client size of 1x1.
If AbstractClient::adjustedSize() is called before the XdgToplevelClient is mapped, it will return 1x1 rather than 0x0 as expected, which will confuse
QSize s = adjustedSize();
if (s != size() && s.isValid())
resizeWithChecks(s);
in AbstractClient::applyWindowRules(). Since 1x1 is different from 0x0, the xdg-toplevel surface is going to be resized to 1x1.