Error in trace file for Dialog Options

When the New Account Hierarchy Assistant is used, the book options are
added to the assistant as a notebook page and so will not have a parent
widget to be used when restoring the window size so test for parent
before using gnc_restore_window_size

gnucash/gnome-utils/dialog-options.c

@@ -2273,7 +2273,8 @@ gnc_options_dialog_new_modal(gboolean modal, gchar *title,
 
     gtk_builder_connect_signals_full (builder, gnc_builder_connect_full_func, retval);
 
-    gnc_restore_window_size (GNC_PREFS_GROUP, GTK_WINDOW(retval->window), parent);
+    if (parent) // when added to a page of the hierarchy assistant there will be no parent
+        gnc_restore_window_size (GNC_PREFS_GROUP, GTK_WINDOW(retval->window), parent);
 
     if (title)
         gtk_window_set_title(GTK_WINDOW(retval->window), title);