Fix warning from MinGW/GCC 6.2

src/widgets/styles/qwindowsvistastyle.cpp: In member function 'virtual QSize QWindowsVistaStyle::sizeFromContents(QStyle::ContentsType, const QStyleOption*, const QSize&, const QWidget*) const':
src/widgets/styles/qwindowsvistastyle.cpp:1872:9: error: this 'if' clause does not guard... [-Werror=misleading-indentation]
         if (!sz.isEmpty())
         ^~
src/widgets/styles/qwindowsvistastyle.cpp:1874:13: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'if'
             return sz;

Change-Id: Ifd3faef8c93f12d5fadaf4edf875fbe0fc6fb785
Reviewed-by: Friedemann Kleint <[email protected]>

src/widgets/styles/qwindowsvistastyle.cpp

@@ -1871,8 +1871,7 @@ QSize QWindowsVistaStyle::sizeFromContents(ContentsType type, const QStyleOption
     case CT_MenuBarItem:
         if (!sz.isEmpty())
             sz += QSize(windowsItemHMargin * 5 + 1, 5);
-            return sz;
-        break;
+        return sz;
 #endif
     case CT_ItemViewItem:
         sz = QWindowsXPStyle::sizeFromContents(type, option, size, widget);