Segfault in random map generator

Start the editor and create a random map. During map creation, Widelands crashes with:

Thread 1 "widelands" received signal SIGSEGV, Segmentation fault.
0x006458bf in Widelands::MapGenerator::create_random_map() ()
(gdb) bt
#0 0x006458bf in Widelands::MapGenerator::create_random_map() ()
#1 0x00622fc7 in MainMenuNewRandomMap::clicked_create_map() ()
#2 0x0074342c in boost::signals2::detail::signal_impl<void (), boost::signals2::optional_last_value<void>, int, std::less<int>, boost::function<void ()>, boost::function<void (boost::signals2::connection const&)>, boost::signals2::mutex>::operator()() ()
#3 0x007ed480 in UI::Button::handle_mouserelease(unsigned char, int, int) ()
#4 0x008062ef in UI::Panel::ui_mouserelease(unsigned char, int, int) ()
#5 0x005cdd80 in WLApplication::handle_input(InputCallback const*) ()
#6 0x008069d9 in UI::Panel::do_run() ()
#7 0x005ef3d0 in EditorInteractive::run_editor(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) ()
#8 0x005d2e7e in WLApplication::run() ()
#9 0x00586d7e in main ()