window: Don't store window to avoid ref cycles

Use root() instead and move one constructor to on root for having the
root available.

src/util.rs

@@ -17,6 +17,7 @@
 // SPDX-License-Identifier: GPL-3.0-or-later
 
 pub mod gettext;
+pub mod root;
 
 use std::ffi::CStr;
 use std::fmt::{Debug, Write};
@@ -261,3 +262,8 @@ pub fn locale_settings() -> LocaleSettings {
         locale_settings
     }
 }
+
+pub enum ErrorType {
+    Loader,
+    General,
+}