Crash when buildhelp icon is clicked twice

Playing bzr8184: when i click a buildhelp icon, got the window to select which building to construct, and then click another (or the same) buildhelp icon, an assertion failed:

widelands: src/ui_basic/unique_window.cc:114: virtual UI::UniqueWindow::~UniqueWindow(): Controletest 'registry_->window == this' faalt.

Thread 1 "widelands" received signal SIGABRT, Aborted.
0xb7fd9ce5 in __kernel_vsyscall ()
(gdb) bt
#0 0xb7fd9ce5 in __kernel_vsyscall ()
#1 0xb7586dc0 in __libc_signal_restore_set (set=0xbfffc990) at ../sysdeps/unix/sysv/linux/nptl-signals.h:79
#2 __GI_raise (sig=6) at ../sysdeps/unix/sysv/linux/raise.c:55
#3 0xb7588287 in __GI_abort () at abort.c:89
#4 0xb757fa17 in __assert_fail_base (fmt=0xb460b3d3 "%s%s%s:%u: %s%sControletest '%s' faalt.\n%n", assertion=0x80e94151 "registry_->window == this",
    file=0x80e940f4 "src/ui_basic/unique_window.cc", line=114,
    function=0x80e941e0 <UI::UniqueWindow::~UniqueWindow()::__PRETTY_FUNCTION__> "virtual UI::UniqueWindow::~UniqueWindow()") at assert.c:92
#5 0xb757fa9b in __GI___assert_fail (assertion=0x80e94151 "registry_->window == this",
    file=0x80e940f4 "src/ui_basic/unique_window.cc", line=114,
    function=0x80e941e0 <UI::UniqueWindow::~UniqueWindow()::__PRETTY_FUNCTION__> "virtual UI::UniqueWindow::~UniqueWindow()") at assert.c:101
#6 0x80a802e3 in UI::UniqueWindow::~UniqueWindow (this=0x833625c0, __in_chrg=<optimized out>)
    at src/ui_basic/unique_window.cc:114
#7 0x80af0b2a in FieldActionWindow::~FieldActionWindow (this=0x833625c0, __in_chrg=<optimized out>)
    at src/wui/fieldaction.cc:261
#8 0x80af0b51 in FieldActionWindow::~FieldActionWindow (this=0x833625c0, __in_chrg=<optimized out>)
    at src/wui/fieldaction.cc:266
#9 0x80a6448b in UI::Panel::check_child_death (this=0x829bcf28) at src/ui_basic/panel.cc:695
#10 0x80a63436 in UI::Panel::do_run (this=0x829bcf28) at src/ui_basic/panel.cc:186
#11 0x807b4540 in UI::Panel::run<UI::Panel::Returncodes> (this=0x829bcf28) at ../src/ui_basic/panel.h:96
#12 0x808c6685 in Widelands::Game::run (this=0xbfffddc4, loader_ui=0xbfffcfd4, start_game_type=Widelands::Game::NewSPScenario, script_to_run="",
    replay=false, prefix_for_replays="single_player") at src/logic/game.cc:525
#13 0x808c43f9 in Widelands::Game::run_splayer_scenario_direct (this=0xbfffddc4, mapname="campaigns/tutorial03_seafaring.wmf", script_to_run="")
    at src/logic/game.cc:233
#14 0x807ad102 in WLApplication::mainmenu_tutorial (this=0x812b4840) at src/wlapplication.cc:1069
#15 0x807acc30 in WLApplication::mainmenu (this=0x812b4840) at src/wlapplication.cc:996
#16 0x807a90b3 in WLApplication::run (this=0x812b4840) at src/wlapplication.cc:442
#17 0x807a73ff in main (argc=1, argv=0xbffff2e4) at src/main.cc:49

Works (i.e. crashes) every time.