[evolution] Prevent crash in cal_data_model_notify_recurrences_cb()

[Milan Crha <mcrha src gnome org>]

commit dfe11038c5b0ae73accde69bf4e098a6d022b77d
Author: Milan Crha <mcrha redhat com>
Date:   Thu May 2 10:23:18 2019 +0200

    Prevent crash in cal_data_model_notify_recurrences_cb()
    
    The ECalDataModel could use the reference to itself in the internal thread
    pool after the thread pool had been freed, together with the data model.
    This change prevents the crash by adding a reference on the data model
    for the whole internal thread run.
    
    Reported downstream at:
    https://bugzilla.redhat.com/show_bug.cgi?id=1705345

 src/calendar/gui/e-cal-data-model.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)
---
diff --git a/src/calendar/gui/e-cal-data-model.c b/src/calendar/gui/e-cal-data-model.c
index 2e2aab826e..dc2b22cbee 100644
--- a/src/calendar/gui/e-cal-data-model.c
+++ b/src/calendar/gui/e-cal-data-model.c
@@ -376,6 +376,7 @@ cal_data_model_emit_view_state_changed (ECalDataModel *data_model,
 typedef void (* InternalThreadJobFunc) (ECalDataModel *data_model, gpointer user_data);
 
 typedef struct _InternalThreadJobData {
+       ECalDataModel *data_model;
        InternalThreadJobFunc func;
        gpointer user_data;
 } InternalThreadJobData;
@@ -384,14 +385,14 @@ static void
 cal_data_model_internal_thread_job_func (gpointer data,
                                         gpointer user_data)
 {
-       ECalDataModel *data_model = user_data;
        InternalThreadJobData *job_data = data;
 
        g_return_if_fail (job_data != NULL);
        g_return_if_fail (job_data->func != NULL);
 
-       job_data->func (data_model, job_data->user_data);
+       job_data->func (job_data->data_model, job_data->user_data);
 
+       g_object_unref (job_data->data_model);
        g_free (job_data);
 }
 
@@ -406,6 +407,7 @@ cal_data_model_submit_internal_thread_job (ECalDataModel *data_model,
        g_return_if_fail (func != NULL);
 
        job_data = g_new0 (InternalThreadJobData, 1);
+       job_data->data_model = g_object_ref (data_model);
        job_data->func = func;
        job_data->user_data = user_data;