reuse a gtk_file_chooser_dialog multiple times - gtk3

Question

I'd like to re-use a gtk_file_chooser_dialog multiple times. But after the user closes the dialog the first time, the pointer to the GtkFileChooserDialog struct seems broken.
Opening the diaglog the first time succeeds.
Opening the same dialog a second time results in
(crystal_facet_uml:3797): GLib-GObject-WARNING **: invalid unclassed pointer in cast to 'GtkWidget'
(crystal_facet_uml:3797): Gtk-CRITICAL **: gtk_widget_show_all: assertion 'GTK_IS_WIDGET (widget)' failed
My first idea was to increase the reference counter on the dialog to prevent it from being cleaed up:
(*this_).use_db_file_chooser = gtk_file_chooser_dialog_new ( "Select DB to use",
GTK_WINDOW( (*this_).window ),
GTK_FILE_CHOOSER_ACTION_SAVE,
"Cancel",
GTK_RESPONSE_CANCEL,
"Create/Use DB-File",
GTK_RESPONSE_ACCEPT,
NULL
);
g_object_ref( (*this_).use_db_file_chooser );
... but this only shifts the problem: the dialog-window seems to stay but the contained widgets are gone:
(crystal_facet_uml:3797): Gtk-CRITICAL **: gtk_container_foreach: assertion 'GTK_IS_CONTAINER (container)' failed
(crystal_facet_uml:3797): Gtk-CRITICAL **: gtk_container_foreach: assertion 'GTK_IS_CONTAINER (container)' failed
(crystal_facet_uml:3797): Gtk-CRITICAL **: gtk_container_foreach: assertion 'GTK_IS_CONTAINER (container)' failed
(crystal_facet_uml:3797): Gtk-CRITICAL **: gtk_container_foreach: assertion 'GTK_IS_CONTAINER (container)' failed
(crystal_facet_uml:3797): Gtk-CRITICAL **: _gtk_file_chooser_embed_initial_focus: assertion 'GTK_IS_FILE_CHOOSER_EMBED (chooser_embed)' failed
Gtk-Message: GtkDialog mapped without a transient parent. This is discouraged.
(crystal_facet_uml:3797): Gtk-CRITICAL **: gtk_container_foreach: assertion 'GTK_IS_CONTAINER (container)' failed
Do you have an idea how to do this right?
(Rationale for re-using the file chooser dialogs are: 1) I want to allocate it in the beginning and afterwards not care about NULL-pointers anymore, 2) I want to keep the contents of the dialog (current folder, current filename), 3) I want to start this non-modal dialog only once, never 2 dialogs at the same time, 4) I want to keep the g_signal bindings throughout the lifetime of my program).
(full source code: https://sourceforge.net/p/crystal-facet-uml/code/ci/46ee183ea06baae3af70d81c74efe767fccc5028/tree/gui/source/gui_main_window.c )

Answer 1

I found a nice solution (with the help of the answer to C GTK can't open Dialog again after closing via ESC and the documentation on https://developer.gnome.org/gtk3/stable/GtkWidget.html#GtkWidget-delete-event ):
simply connect the delete-event of the dialog to the gtk-predefined callback function gtk_widget_hide_on_delete():
g_signal_connect( G_OBJECT((*this_).use_db_file_chooser), "delete-event", G_CALLBACK(gtk_widget_hide_on_delete), NULL );
And your dialog-object is not destroyed when the user closes it.