[gnome-calendar/mcatanzaro/rbz-1509551] Try to fix a crash in update_default_calendar_row()

[Michael Catanzaro <mcatanzaro src gnome org>]

commit 95ad7346238b899a6c826b0d67460187170ff80c
Author: Michael Catanzaro <mcatanzaro igalia com>
Date:   Tue Jul 2 12:16:43 2019 -0500

    Try to fix a crash in update_default_calendar_row()
    
    This function is crashing in 3.32 because the manager object is invalid.
    I think there are two related bugs:
    
    First, it looks like gcal_quick_add_popover_set_property() is failing to
    disconnect its signals from the old GcalManager before setting the new
    one. In one backtrace, I see the GcalManager emitting the signal is
    different than the GcalQuickAddPopover's current manager, which is
    surely unintended.
    
    But that shouldn't be enough to crash on its own, since the
    GcalQuickAddPopover should still have a valid manager, even if not the
    intended one. So I suspect the GcalQuickAddPopover itself is invalid at
    this point. (The crash occured for me after adding an event, so it was
    probably just destroyed.) GcalQuickAddPopover is not disconnecting these
    signals in dispose, which is unsafe. We can avoid the need to do so by
    using g_signal_connect_object().
    
    Now in master, the GcalManager is now owned indirectly by the GcalContext,
    but the underlying problems from the 3.32 crash are all still here. This
    attempts to fix them. The fix is speculative, but it's surely safer than
    the original code.
    
    Hopefully fixes #416
    
    https://bugzilla.redhat.com/show_bug.cgi?id=1509551

 src/gui/gcal-quick-add-popover.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)
---
diff --git a/src/gui/gcal-quick-add-popover.c b/src/gui/gcal-quick-add-popover.c
index a1d7a4cf..d5aaaaed 100644
--- a/src/gui/gcal-quick-add-popover.c
+++ b/src/gui/gcal-quick-add-popover.c
@@ -782,12 +782,17 @@ gcal_quick_add_popover_set_property (GObject      *object,
       break;
 
     case PROP_CONTEXT:
-      if (g_set_object (&self->context, g_value_get_object (value)))
+      if (self->context != g_value_get_object (value))
         {
           g_autoptr (GList) calendars = NULL;
           GcalManager *manager;
           GList *l;
 
+          manager = gcal_context_get_manager (self->context);
+          g_signal_handlers_disconnect_by_data (manager, self);
+
+          g_set_object (&self->context, g_value_get_object (value));
+
           /* Add currently loaded sources */
           manager = gcal_context_get_manager (self->context);
           calendars = gcal_manager_get_calendars (manager);
@@ -798,10 +803,10 @@ gcal_quick_add_popover_set_property (GObject      *object,
           g_list_free (calendars);
 
           /* Connect to the manager signals and keep the list updates */
-          g_signal_connect (manager, "calendar-added", G_CALLBACK (on_calendar_added), self);
-          g_signal_connect (manager, "calendar-changed", G_CALLBACK (on_calendar_changed), self);
-          g_signal_connect (manager, "calendar-removed", G_CALLBACK (on_calendar_removed), self);
-          g_signal_connect_swapped (manager, "notify::default-calendar", G_CALLBACK 
(update_default_calendar_row), self);
+          g_signal_connect_object (manager, "calendar-added", G_CALLBACK (on_calendar_added), self, 0);
+          g_signal_connect_object (manager, "calendar-changed", G_CALLBACK (on_calendar_changed), self, 0);
+          g_signal_connect_object (manager, "calendar-removed", G_CALLBACK (on_calendar_removed), self, 0);
+          g_signal_connect_object (manager, "notify::default-calendar", G_CALLBACK 
(update_default_calendar_row), self, G_CONNECT_SWAPPED);
 
           g_signal_connect_object (self->context,
                                    "notify::time-format",