Fix missing initializer warning in gobject/tests/dynamictests.c:test_module_get_type()

gobject/tests/dynamictests.c: In function ‘test_module_get_type’:
gobject/tests/dynamictests.c:97:7: error: missing initializer for field ‘value_table’ of ‘GTypeInfo’ {aka ‘const struct _GTypeInfo’}
   97 |       };
      |       ^
In file included from gobject/gobject.h:24,
                 from gobject/gbinding.h:29,
                 from glib/glib-object.h:22,
                 from gobject/tests/dynamictests.c:23:
gobject/gtype.h:1063:26: note: ‘value_table’ declared here
 1063 |   const GTypeValueTable *value_table;
      |                          ^~~~~~~~~~~

gobject/tests/dynamictests.c

@@ -93,7 +93,8 @@ static GType test_module_get_type (void)
 	NULL,
 	sizeof (TestModule),
 	0,
-	(GInstanceInitFunc)NULL
+        (GInstanceInitFunc)NULL,
+        NULL,
       };
     object_type = g_type_register_static (G_TYPE_TYPE_MODULE, "TestModule", &object_info, 0);
   }