[epiphany] Only show unresponsive page dialog on affected page

[Marge Bot <marge-bot src gnome org>]

commit 7d8ceb3c94f34d7ce27676f491ccf85e5519b0c2
Author: Jan-Michael Brummer <jan brummer tabos org>
Date:   Tue Aug 17 22:34:03 2021 +0200

    Only show unresponsive page dialog on affected page
    
    Fixes: https://gitlab.gnome.org/GNOME/epiphany/-/issues/1583
    Part-of: <https://gitlab.gnome.org/GNOME/epiphany/-/merge_requests/1009>

 embed/ephy-web-view.c | 3 +++
 1 file changed, 3 insertions(+)
---
diff --git a/embed/ephy-web-view.c b/embed/ephy-web-view.c
index 031316a6f..fe1fbf827 100644
--- a/embed/ephy-web-view.c
+++ b/embed/ephy-web-view.c
@@ -871,6 +871,9 @@ unresponsive_process_timeout_cb (gpointer user_data)
 {
   EphyWebView *web_view = EPHY_WEB_VIEW (user_data);
 
+  if (!gtk_widget_get_mapped (GTK_WIDGET (web_view)))
+    return G_SOURCE_CONTINUE;
+
   web_view->unresponsive_process_dialog = gtk_message_dialog_new (GTK_WINDOW (gtk_widget_get_toplevel 
(GTK_WIDGET (web_view))),
                                                                   GTK_DIALOG_MODAL | 
GTK_DIALOG_DESTROY_WITH_PARENT | GTK_DIALOG_USE_HEADER_BAR,
                                                                   GTK_MESSAGE_QUESTION,