[unicode] Simplify method setting

src/hb-unicode.cc

@@ -206,14 +206,10 @@ hb_unicode_funcs_set_##name##_func (hb_unicode_funcs_t             *ufuncs,    \
     ufuncs->get.name = func;                                                   \
     ufuncs->user_data.name = user_data;                                        \
     ufuncs->destroy.name = destroy;                                            \
-  } else if (ufuncs->parent != NULL) {                                         \
+  } else {                                                                     \
     ufuncs->get.name = ufuncs->parent->get.name;                               \
     ufuncs->user_data.name = ufuncs->parent->user_data.name;                   \
     ufuncs->destroy.name = NULL;                                               \
-  } else {                                                                     \
-    ufuncs->get.name = hb_unicode_get_##name##_nil;                            \
-    ufuncs->user_data.name = NULL;                                             \
-    ufuncs->destroy.name = NULL;                                               \
   }                                                                            \
 }                                                                              \
                                                                                \

test/test-unicode.c

@@ -482,6 +482,7 @@ test_unicode_properties (gconstpointer user_data)
   gboolean failed = TRUE;
 
   g_assert (hb_unicode_funcs_is_immutable (uf));
+  g_assert (hb_unicode_funcs_get_parent (uf));
 
   for (i = 0; i < G_N_ELEMENTS (properties); i++) {
     const property_t *p = &properties[i];
@@ -609,6 +610,9 @@ test_unicode_setters (void)
     g_assert_cmphex (p->getter (uf, 'a'), ==, HB_SCRIPT_LATIN);
     g_assert_cmphex (p->getter (uf, '0'), ==, HB_SCRIPT_UNKNOWN);
 
+    p->func_setter (uf, (get_func_t) NULL, NULL, NULL);
+    g_assert (data[0].freed && !data[1].freed);
+
     g_assert (!hb_unicode_funcs_is_immutable (uf));
     hb_unicode_funcs_make_immutable (uf);
     g_assert (hb_unicode_funcs_is_immutable (uf));
@@ -616,7 +620,7 @@ test_unicode_setters (void)
     /* Since uf is immutable now, the following setter should do nothing. */
     p->func_setter (uf, (get_func_t) a_is_for_arabic_get_script, &data[1], free_up);
 
-    g_assert (!data[0].freed && !data[1].freed);
+    g_assert (data[0].freed && !data[1].freed);
     hb_unicode_funcs_destroy (uf);
     g_assert (data[0].freed && !data[1].freed);