[gnome-control-center] keyboard-shortcut-editor: fix leak of accel string

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit 8355404ed4694860a76ffe8707f903de43fa8566
Author: Victor Toso <victortoso redhat com>
Date:   Tue Oct 12 14:09:45 2021 +0200

    keyboard-shortcut-editor: fix leak of accel string
    
    ==31571== 120 bytes in 8 blocks are definitely lost in loss record 17,034 of 19,290
    ==31571==    at 0x484086F: malloc (vg_replace_malloc.c:380)
    ==31571==    by 0x4AF77A8: g_malloc (gmem.c:106)
    ==31571==    by 0x4D9816A: gtk_accelerator_name (gtkaccelgroup.c:1577)
    ==31571==    by 0x4A82D1: setup_custom_shortcut (cc-keyboard-shortcut-editor.c:364)
    ==31571==    by 0x4A92DF: cc_keyboard_shortcut_editor_key_press_event (cc-keyboard-shortcut-editor.c:745)

 panels/keyboard/cc-keyboard-shortcut-editor.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/panels/keyboard/cc-keyboard-shortcut-editor.c b/panels/keyboard/cc-keyboard-shortcut-editor.c
index 8d3546d0e..25441f194 100644
--- a/panels/keyboard/cc-keyboard-shortcut-editor.c
+++ b/panels/keyboard/cc-keyboard-shortcut-editor.c
@@ -309,7 +309,7 @@ setup_custom_shortcut (CcKeyboardShortcutEditor *self)
   HeaderMode mode;
   gboolean is_custom, is_accel_empty;
   gboolean valid, accel_valid;
-  gchar *accel;
+  g_autofree char *accel = NULL;
 
   is_custom = is_custom_shortcut (self);
   accel_valid = is_valid_binding (self->custom_combo) &&