QWidget::showFullScreen() crashes if widget has 0 margins layout.
Doesn't crash on qt4 or when margin != 0.

The minimal example to reproduce the crash:

#include <QApplication>
#include <QWidget>
#include <QBoxLayout>

int main(int argc, char *argv[])
{

    QApplication a(argc, argv);
    QWidget w;

    QBoxLayout *layout = new QVBoxLayout;
    layout->setMargin(0);
    w.setLayout(layout);
    w.showFullScreen();
    
    return a.exec();
}

Backtrace:

0 CoreFoundation 0x00007fff97fcdfc6 __exceptionPreprocess + 198
1 libobjc.A.dylib 0x00007fff9444fd5e objc_exception_throw + 43
2 CoreFoundation 0x00007fff97fcddfa +[NSException raise:format:arguments:] + 106
3 Foundation 0x00007fff982e4743 -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:] + 169
4 AppKit 0x00007fff8fb37162 -[_NSFullScreenTransition makeAndSetupOverlayWindow] + 269
5 AppKit 0x00007fff8fb39517 -[_NSWindowFullScreenTransition enterFullScreenTransitionForWindow:animated:activatingIt:] + 505
6 AppKit 0x00007fff8f4b0223 -[NSWindow _enterFullScreenMode:animating:activating:] + 275
7 libqcocoa.dylib 0x000000010170a5ef _ZN12QCocoaWindow15syncWindowStateEN2Qt11WindowStateE + 143
8 libqcocoa.dylib 0x000000010170a341 _ZN12QCocoaWindow10setVisibleEb + 321
9 QtGui 0x0000000100688e23 _ZN7QWindow10setVisibleEb + 211
10 QtWidgets 0x0000000100083b7d _ZN14QWidgetPrivate8show_sysEv + 957
11 QtWidgets 0x000000010006766e _ZN14QWidgetPrivate11show_helperEv + 398
12 QtWidgets 0x0000000100067f9c _ZN7QWidget10setVisibleEb + 684
13 QtWidgets 0x000000010005e5a4 _ZN7QWidget14showFullScreenEv + 52
14 fullscreen_test 0x00000001000034e3 main + 195