libmsi: guard calls of parent class constructed method

RHEL6's glib 2.22 leaves a NULL pointer there.

Author: bonzini

libmsi/libmsi-database.c

@@ -101,7 +101,8 @@ libmsi_database_init (LibmsiDatabase *self)
 static void
 libmsi_database_constructed (GObject *object)
 {
-    G_OBJECT_CLASS (libmsi_database_parent_class)->constructed (object);
+    if (G_OBJECT_CLASS (libmsi_database_parent_class)->constructed)
+        G_OBJECT_CLASS (libmsi_database_parent_class)->constructed (object);
 }
 
 static void

libmsi/libmsi-query.c

@@ -107,7 +107,8 @@ libmsi_query_get_property (GObject *object, guint prop_id, GValue *value, GParam
 static void
 libmsi_query_constructed (GObject *object)
 {
-    G_OBJECT_CLASS (libmsi_query_parent_class)->constructed (object);
+    if (G_OBJECT_CLASS (libmsi_query_parent_class)->constructed)
+        G_OBJECT_CLASS (libmsi_query_parent_class)->constructed (object);
 }
 
 static void

libmsi/libmsi-record.c

@@ -122,7 +122,8 @@ libmsi_record_constructed (GObject *object)
     // FIXME: +1 could be removed if accessing with idx-1
     self->fields = g_new0 (LibmsiField, self->count + 1);
 
-    G_OBJECT_CLASS (libmsi_record_parent_class)->constructed (object);
+    if (G_OBJECT_CLASS (libmsi_record_parent_class)->constructed)
+        G_OBJECT_CLASS (libmsi_record_parent_class)->constructed (object);
 }
 
 static void

libmsi/libmsi-summary-info.c

@@ -128,7 +128,8 @@ libmsi_summary_info_constructed (GObject *object)
         }
     }
 
-    G_OBJECT_CLASS (libmsi_summary_info_parent_class)->constructed (object);
+    if (G_OBJECT_CLASS (libmsi_summary_info_parent_class)->constructed)
+        G_OBJECT_CLASS (libmsi_summary_info_parent_class)->constructed (object);
 }
 
 static void