Fix ibuffer loading error.

CHANGELOG.md

@@ -6,6 +6,13 @@ Perspective was started in 2008 and this log was only added in 2021.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 
+## Unreleased
+
+### Fixed
+
+- `persp-ibuffer-generate-filter-groups`: load `ibuf-ext` library if needed ([#202](https://github.com/nex3/perspective-el/issues/202)).
+
+
 ## [2.18] — 2022-09-20
 
 ### Added

perspective.el

@@ -2215,6 +2215,8 @@ were merged in from a previous call to `persp-merge'."
 ;;;###autoload
 (defun persp-ibuffer-generate-filter-groups ()
   "Create a set of ibuffer filter groups based on the persp name of buffers."
+  (unless (featurep 'ibuf-ext)
+    (require 'ibuf-ext))
   (declare-function ibuffer-remove-duplicates "ibuf-ext.el")
   (declare-function ibuffer-push-filter "ibuf-ext.el")
   (declare-function ibuffer-pop-filter "ibuf-ext.el")