Use of deallocated memory from statistics menu

When closing the statistics menu (window with 4 buttons)
and closing one of the other statistics menus. The code
tries to change the style of a button that has already beend freed:

==39835==ERROR: AddressSanitizer: heap-use-after-free on address 0x613000a7fdc4 at pc 0x00010236a898 bp 0x7ffeee7bd4d0 sp 0x7ffeee7bd4c8
WRITE of size 4 at 0x613000a7fdc4 thread T0
    #0 0x10236a897 in UI::Button::set_style(UI::Button::Style) (/Users/klaus/develop/widelands-repo/bug_1730204-crash/./widelands:x86_64+0x100f36897)
...
    #7 0x10253f36b in UI::UniqueWindow::~UniqueWindow() (/Users/klaus/develop/widelands-repo/bug_1730204-crash/./widelands:x86_64+0x10110b36b)
    #8 0x102990787 in GeneralStatisticsMenu::~GeneralStatisticsMenu() (/Users/klaus/develop/widelands-repo/bug_1730204-crash/./widelands:x86_64+0x10155c787)

0x613000a7fdc4 is located 260 bytes inside of 328-byte region [0x613000a7fcc0,0x613000a7fe08)
freed by thread T0 here:
    #1 0x102361701 in UI::Button::~Button() (/Users/klaus/develop/widelands-repo/bug_1730204-crash/./widelands:x86_64+0x100f2d701)
    #2 0x10246fd77 in UI::Panel::free_children() (/Users/klaus/develop/widelands-repo/bug_1730204-crash/./widelands:x86_64+0x10103bd77)
..
    #6 0x1028e5cc3 in GameStatisticsMenu::~GameStatisticsMenu() (/Users/klaus/develop/widelands-repo/bug_1730204-crash/./widelands:x86_64+0x1014b1cc3)

reviously allocated by thread T0 here:
    #1 0x1028e3fae in GameStatisticsMenu::add_button(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, std::__1::basic_string<char, std::__1::c

This will result in memory corruption with +/- bad results.
The same will happen if you reopen any statics menu, so
keeping the window open as a workaround will not help.

I will spend some hour now to find some workaround, but maybe this is broken by design.