@Seth, yes, it reproduces for me on master.  It's throwing an exception in NSRunModal, but my debugger won't tell me what:

__cxa_throw 0x00007fff660c61f7
objc_exception_throw 0x00007fff674eada5
+[NSException raise:format:] 0x00007fff402f017d
_NSRunModal 0x00007fff3e037431
-[NSApplication runModalSession:] 0x00007fff3db89a9b
wxGUIEventLoop::DoDispatchTimeout(unsigned long) evtloop.mm:213
wxCFEventLoop::DispatchTimeout(unsigned long) evtloop_cf.cpp:259
wxCFEventLoop::DoProcessEvents() evtloop_cf.cpp:246
wxCFEventLoop::OSXDoRun() evtloop_cf.cpp:304
wxModalEventLoop::OSXDoRun() evtloop.mm:436
wxCFEventLoop::DoRun() evtloop_cf.cpp:340
wxEventLoopBase::Run() evtloopcmn.cpp:78
wxModalEventLoop::Run() evtloop.h:33
wxDialog::ShowModal() dialog_osx.cpp:150
FOOTPRINT_WIZARD_FRAME::SelectFootprintWizard() footprint_wizard_frame_functions.cpp:170
FOOTPRINT_WIZARD_FRAME::OnActivate(wxActivateEvent&) footprint_wizard_frame.cpp:534
wxAppConsoleBase::HandleEvent(wxEvtHandler*, void (wxEvtHandler::*)(wxEvent&), wxEvent&) const appbase.cpp:611
wxAppConsoleBase::CallEventHandler(wxEvtHandler*, wxEventFunctor&, wxEvent&) const appbase.cpp:623
wxEvtHandler::ProcessEventIfMatchesId(wxEventTableEntryBase const&, wxEvtHandler*, wxEvent&) event.cpp:1395
wxEventHashTable::HandleEvent(wxEvent&, wxEvtHandler*) event.cpp:1001
wxEvtHandler::TryHereOnly(wxEvent&) event.cpp:1592
wxEvtHandler::TryBeforeAndHere(wxEvent&) event.h:3680
wxEvtHandler::ProcessEvent(wxEvent&) event.cpp:1494
EDA_BASE_FRAME::ProcessEvent(wxEvent&) eda_base_frame.cpp:183
wxEvtHandler::DoTryChain(wxEvent&) event.cpp:1557
wxEvtHandler::ProcessEventLocally(wxEvent&) event.cpp:1525
wxEvtHandler::ProcessEvent(wxEvent&) event.cpp:1498
wxEvtHandler::SafelyProcessEvent(wxEvent&) event.cpp:1616
wxWindowBase::HandleWindowEvent(wxEvent&) const wincmn.cpp:1525
wxNonOwnedWindow::HandleActivated(double, bool) nonownedwnd_osx.cpp:306
::-[wxNonOwnedWindowController windowDidBecomeKey:](NSNotification *) nonownedwnd.mm:491
__CFNOTIFICATIONCENTER_IS_CALLING_OUT_TO_AN_OBSERVER__ 0x00007fff401ed62c
_CFXRegistrationPost 0x00007fff401ed4fa
___CFXNotificationPost_block_invoke 0x00007fff401ed231
-[_CFXNotificationRegistrar find:object:observer:enumerator:] 0x00007fff401ab010
_CFXNotificationPost 0x00007fff401aa147
-[NSNotificationCenter postNotificationName:object:userInfo:] 0x00007fff422bb817
-[NSWindow becomeKeyWindow] 0x00007fff3d894973
-[NSWindow _changeKeyAndMainLimitedOK:] 0x00007fff3d893bcd
-[NSWindow _makeKeyRegardlessOfVisibility] 0x00007fff3d94127e
NSPerformVisuallyAtomicChange 0x00007fff3d896c0c
-[NSWindow makeKeyAndOrderFront:] 0x00007fff3d9411b5
wxNonOwnedWindowCocoaImpl::Show(bool) nonownedwnd.mm:779
wxNonOwnedWindow::Show(bool) nonownedwnd_osx.cpp:377
KIWAY_PLAYER::ShowModal(wxString*, wxWindow*) kiway_player.cpp:100
FOOTPRINT_EDIT_FRAME::Process_Special_Functions(wxCommandEvent&) footprint_editor_utils.cpp:222
MODULE_EDITOR_TOOLS::CreateFootprint(TOOL_EVENT const&) footprint_editor_tools.cpp:133
int std::__1::__invoke_void_return_wrapper<int>::__call<std::__1::__bind<int (MODULE_EDITOR_TOOLS::*&)(TOOL_EVENT const&), MODULE_EDITOR_TOOLS*, std::__1::placeholders::__ph<1> const&>&, TOOL_EVENT const&>(std::__1::__bind<int (MODULE_EDITOR_TOOLS::*&)(TOOL_EVENT const&), MODULE_EDITOR_TOOLS*, std::__1::placeholders::__ph<1> const&>&, TOOL_EVENT const&) type_traits:4369
int std::__1::__invoke_void_return_wrapper<int>::__call<std::__1::__bind<int (MODULE_EDITOR_TOOLS::*&)(TOOL_EVENT const&), MODULE_EDITOR_TOOLS*, std::__1::placeholders::__ph<1> const&>&, TOOL_EVENT const&>(std::__1::__bind<int (MODULE_EDITOR_TOOLS::*&)(TOOL_EVENT const&), MODULE_EDITOR_TOOLS*, std::__1::placeholders::__ph<1> const&>&, TOOL_EVENT const&) functional:2216
int std::__1::__invoke_void_return_wrapper<int>::__call<std::__1::__bind<int (MODULE_EDITOR_TOOLS::*&)(TOOL_EVENT const&), MODULE_EDITOR_TOOLS*, std::__1::placeholders::__ph<1> const&>&, TOOL_EVENT const&>(std::__1::__bind<int (MODULE_EDITOR_TOOLS::*&)(TOOL_EVENT const&), MODULE_EDITOR_TOOLS*, std::__1::placeholders::__ph<1> const&>&, TOOL_EVENT const&) functional:2249
int std::__1::__invoke_void_return_wrapper<int>::__call<std::__1::__bind<int (MODULE_EDITOR_TOOLS::*&)(TOOL_EVENT const&), MODULE_EDITOR_TOOLS*, std::__1::placeholders::__ph<1> const&>&, TOOL_EVENT const&>(std::__1::__bind<int (MODULE_EDITOR_TOOLS::*&)(TOOL_EVENT const&), MODULE_EDITOR_TOOLS*, std::__1::placeholders::__ph<1> const&>&, TOOL_EVENT const&) type_traits:4428
int std::__1::__invoke_void_return_wrapper<int>::__call<std::__1::__bind<int (MODULE_EDITOR_TOOLS::*&)(TOOL_EVENT const&), MODULE_EDITOR_TOOLS*, std::__1::placeholders::__ph<1> const&>&, TOOL_EVENT const&>(std::__1::__bind<int (MODULE_EDITOR_TOOLS::*&)(TOOL_EVENT const&), MODULE_EDITOR_TOOLS*, std::__1::placeholders::__ph<1> const&>&, TOOL_EVENT const&) __functional_base:318
std::__1::__function::__func<std::__1::__bind<int (MODULE_EDITOR_TOOLS::*&)(TOOL_EVENT const&), MODULE_EDITOR_TOOLS*, std::__1::placeholders::__ph<1> const&>, std::__1::allocator<std::__1::__bind<int (MODULE_EDITOR_TOOLS::*&)(TOOL_EVENT const&), MODULE_EDITOR_TOOLS*, std::__1::placeholders::__ph<1> const&> >, int (TOOL_EVENT const&)>::operator()(TOOL_EVENT const&) functional:1562
std::__1::function<int (TOOL_EVENT const&)>::operator()(TOOL_EVENT const&) const functional:1913
COROUTINE<int, TOOL_EVENT const&>::callerStub(long) coroutine.h:331
make_fcontext 0x000000012031be2a