Revert "libgimp, libgimpconfig: gimp_config_deserialize_file() should not…"

This reverts commit 73c0ee8da7.

Actually I was wrong, there was a bug in gimpconfig-deserialize.c. See
coming commit.

libgimp/gimpprocedureconfig.c

@@ -981,8 +981,7 @@ gimp_procedure_config_load_last (GimpProcedureConfig  *config,
                                           file,
                                           NULL, error);
 
-  if (! success && error && *error &&
-      (*error)->code == GIMP_CONFIG_ERROR_OPEN_ENOENT)
+  if (! success && (*error)->code == GIMP_CONFIG_ERROR_OPEN_ENOENT)
     {
       g_clear_error (error);
     }

libgimpconfig/gimpconfig-iface.c

@@ -494,6 +494,9 @@ gimp_config_deserialize_file (GimpConfig  *config,
 
   gimp_scanner_unref (scanner);
 
+  if (! success)
+    g_assert (error == NULL || *error != NULL);
+
   return success;
 }
 

libgimpconfig/gimpconfig-iface.h

@@ -40,9 +40,6 @@ struct _GimpConfigInterface
   gboolean     (* serialize)            (GimpConfig       *config,
                                          GimpConfigWriter *writer,
                                          gpointer          data);
-  /* TODO: we should add a GError** parameter to the deserialize()
-   * method in order to be able to report errors.
-   */
   gboolean     (* deserialize)          (GimpConfig       *config,
                                          GScanner         *scanner,
                                          gint              nest_level,