Default modeline segments to :init

Fixes buffer-id in non-file-visiting buffers.

modules/ui/modeline/autoload/settings.el

@@ -79,7 +79,7 @@ keep them left and right aligned respectively."
                    (if (eq realvar name)
                        `((defvar-local ,name nil ,docstring)
                          (setq-default ,name ,init))
-                     `((defvar-local ,realvar nil)
+                     `((defvar-local ,realvar ,init)
                        (defvar-local ,name nil ,docstring)
                        (setq-default
                         ,name '(:eval (cond ((active) ,realvar)

modules/ui/modeline/config.el

@@ -291,6 +291,7 @@ buffers.")
 
 (def-modeline-segment! +modeline-buffer-id
   :on-hooks (find-file-hook after-save-hook after-revert-hook)
+  :init "%b"
   :faces t
   (if buffer-file-name
       (funcall +modeline-buffer-path-function buffer-file-name)