Fix reading floating window flags from >=1.6 layouts

1.7 introduced per-floating-window "flags" in the saved layouts. When
that value is not present in the saved layout, we need to fallback from
reading from Config global settings

tests/tst_docks.cpp

@@ -8000,7 +8000,5 @@ void TestDocks::tst_restoreFlagsFromVersion16()
 
     auto floatingWindow = dock1->floatingWindow();
     QVERIFY(floatingWindow);
-
-    QEXPECT_FAIL("", "Fixing", Continue);
     QCOMPARE(floatingWindow->floatingWindowFlags(), FloatingWindowFlag::HideTitleBarWhenTabsVisible);
 }