fix: Home start shows Prepare or a blank window, and Prepare opens slowly (#15878)

src/slic3r/GUI/Widgets/WebView.cpp

@@ -10,6 +10,7 @@
 
 #include <wx/webviewarchivehandler.h>
 #include <wx/webviewfshandler.h>
+#include <wx/weakref.h>
 #if wxUSE_WEBVIEW_EDGE
 #include <wx/msw/webview_edge.h>
 #elif defined(__WXMAC__)
@@ -235,7 +236,9 @@ class FakeWebView : public wxWebView
 wxDEFINE_EVENT(EVT_WEBVIEW_RECREATED, wxCommandEvent);
 
 static std::vector<wxWebView*> g_webviews;
-static std::vector<wxWebView*> g_delay_webviews;
+// Webviews waiting for their script handler while another one is added; adding it yields, so a
+// view can be destroyed while it waits.
+static std::vector<wxWeakRef<wxWebView>> g_delay_webviews;
 
 class WebViewRef : public wxObjectRefData
 {
@@ -340,8 +343,9 @@ wxWebView* WebView::CreateWebView(wxWindow * parent, wxString const & url)
                 addScriptMessageHandler(webView);
                 while (!g_delay_webviews.empty()) {
                     auto views = std::move(g_delay_webviews);
-                    for (auto wv : views)
-                        addScriptMessageHandler(wv);
+                    for (const wxWeakRef<wxWebView>& wv : views)
+                        if (wv)
+                            addScriptMessageHandler(wv.get());
                 }
             }
 #ifndef __WIN32__