and fix a memory leak in NotebookbarTabControl where it was not freeing
it's m_pListener field

Change-Id: Ib9970c9084982d532fa38d1bc3c44180ab2c3c39
Reviewed-on: https://gerrit.libreoffice.org/39036Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>