fix to double row problenm in TabBar

After the DPI change, the tab bar showed an unexpected behaviour: on
double button row, the window size was wrong, overlapping content and
tab bar; the sort function from tab bar must be called before getting
the window dimentions, but windowDimensions() required the tabBar
width... in fact 2 variables are wrong, and I should remove them,
_windowWidth and _windowHeight