[gtk] Non-fast-forward update to branch gbsneto/issue-1258

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

The branch 'gbsneto/issue-1258' was changed in a way that was not a fast-forward update.
NOTE: This may cause problems for people pulling from the branch. For more information,
please see:

 https://wiki.gnome.org/Git/Help/NonFastForward

Commits removed from the branch:

  229d708... listbox: Unparent child after removing from sequence

Commits added to the branch:

  5596fea... listbox: Store child iter in a variable when removing