crash on toggle of live preview (all extensions?)

[Tom Davidson]

In today's SVN (rev 17284), under Linux, I can trigger a crash in every extension I've tried with the following steps:

1) Open Inkscape to a new document

2) Select an extension with a dialog box (e.g. Lorem Ipsum)

3) Toggle 'Live Preview' to on
-->warning to console: "** (inkscape:28900): CRITICAL **: void Inkscape::GC::Anchored::release() const: assertion `_anchor' failed

4) Click 'Close' on the extension dialog (note the dialog does not close)

5) Untoggle 'Live Preview'
--> Crash. Backtrace pasted below:

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread -1208486176 (LWP 28900)]
0x00a57ceb in g_main_loop_quit () at ui/widget/random.h:23
23 {
(gdb) bt
#0 0x00a57ceb in g_main_loop_quit () at ui/widget/random.h:23
#1 0x046c0125 in Glib::MainLoop::quit () at ui/widget/random.h:23
#2 0x0850a49e in Inkscape::Extension::ExecutionEnv::livePreview (this=0xb86a260, state=false)
    at extension/execution-env.cpp:302
#3 0x0850befc in Inkscape::Extension::PrefDialog::preview_toggle (this=0xb753340) at extension/prefdialog.cpp:161
#4 0x084ffe82 in Inkscape::Extension::ParamBoolCheckButton::on_toggle (this=0xbc35098)
    at /usr/include/sigc++-2.0/sigc++/signal.h:544
#5 0x046c557a in Glib::SignalProxyNormal::slot0_void_callback () at ui/widget/random.h:23
#6 0x00ae40f9 in g_cclosure_marshal_VOID__VOID () at ui/widget/random.h:23
#7 0x00ad6d9b in g_closure_invoke () at ui/widget/random.h:23
#8 0x00ae7721 in g_signal_chain_from_overridden () at ui/widget/random.h:23
#9 0x00ae8957 in g_signal_emit_valist () at ui/widget/random.h:23
#10 0x00ae8b19 in g_signal_emit () at ui/widget/random.h:23
#11 0x003094c3 in gtk_toggle_button_toggled () at ui/widget/random.h:23
#12 0x00309538 in gtk_toggle_button_toggled () at ui/widget/random.h:23
#13 0x04e2f7e9 in Gtk::Button::on_clicked () at ui/widget/random.h:23
#14 0x04e2ede6 in Gtk::Button_Class::clicked_callback () at ui/widget/random.h:23
#15 0x00ae40f9 in g_cclosure_marshal_VOID__VOID () at ui/widget/random.h:23
#16 0x00ad5589 in g_value_set_static_boxed () at ui/widget/random.h:23
#17 0x00ad6d9b in g_closure_invoke () at ui/widget/random.h:23
#18 0x00ae78ca in g_signal_chain_from_overridden () at ui/widget/random.h:23
#19 0x00ae8957 in g_signal_emit_valist () at ui/widget/random.h:23
#20 0x00ae8b19 in g_signal_emit () at ui/widget/random.h:23
#21 0x00172d63 in gtk_button_clicked () at ui/widget/random.h:23
#22 0x00309298 in gtk_toggle_action_new () at ui/widget/random.h:23
#23 0x04e2f849 in Gtk::Button::on_released () at ui/widget/random.h:23
#24 0x04e2ee96 in Gtk::Button_Class::released_callback () at ui/widget/random.h:23
#25 0x00ae40f9 in g_cclosure_marshal_VOID__VOID () at ui/widget/random.h:23
#26 0x00ad5589 in g_value_set_static_boxed () at ui/widget/random.h:23
#27 0x00ad6d9b in g_closure_invoke () at ui/widget/random.h:23
#28 0x00ae78ca in g_signal_chain_from_overridden () at ui/widget/random.h:23
#29 0x00ae8957 in g_signal_emit_valist () at ui/widget/random.h:23
#30 0x00ae8b19 in g_signal_emit () at ui/widget/random.h:23
#31 0x00172df3 in gtk_button_released () at ui/widget/random.h:23
#32 0x00172e51 in gtk_button_released () at ui/widget/random.h:23
#33 0x04ef1e7c in Gtk::Widget::on_button_release_event () at ui/widget/random.h:23
#34 0x04eef869 in Gtk::Widget_Class::button_release_event_callback () at ui/widget/random.h:23
#35 0x00244650 in gtk_marshal_BOOLEAN__VOID () at ui/widget/random.h:23
#36 0x00ad5589 in g_value_set_static_boxed () at ui/widget/random.h:23
#37 0x00ad6d9b in g_closure_invoke () at ui/widget/random.h:23
#38 0x00ae7a83 in g_signal_chain_from_overridden () at ui/widget/random.h:23
#39 0x00ae871f in g_signal_emit_valist () at ui/widget/random.h:23
---Type <return> to continue, or q <return> to quit---
#40 0x00ae8b19 in g_signal_emit () at ui/widget/random.h:23
#41 0x00359408 in gtk_widget_get_default_style () at ui/widget/random.h:23
#42 0x0023da13 in gtk_propagate_event () at ui/widget/random.h:23
#43 0x0023ec17 in gtk_main_do_event () at ui/widget/random.h:23
#44 0x004f047a in gdk_add_client_message_filter () at ui/widget/random.h:23
#45 0x00a59442 in g_main_context_dispatch () at ui/widget/random.h:23
#46 0x00a5c41f in g_main_context_check () at ui/widget/random.h:23
#47 0x00a5c7c9 in g_main_loop_run () at ui/widget/random.h:23
#48 0x0023f094 in gtk_main () at ui/widget/random.h:23
#49 0x04e75047 in Gtk::Main::run_impl () at ui/widget/random.h:23
#50 0x04e74e32 in Gtk::Main::run () at ui/widget/random.h:23
#51 0x0807ce27 in sp_main_gui (argc=1, argv=0xbfc1b4f4) at main.cpp:724
#52 0x081cfc13 in Inkscape::NSApplication::Application::run (this=0xbfc1b434) at application/application.cpp:117
#53 0x0807cbeb in main (argc=1, argv=0xbfc1b4f4) at main.cpp:539
(gdb)