Regressions from commit 45519023 ("Resolves: tdf#119997
toolbar layout unlock doesn't refresh ui"), commit c5977a89
("Resolves: tdf#96451 do magic to enable embedded chart sidebar
only for chart") and commit faed29ca ("for now show chart
sidebar").

It also adds an assert for the underflow, as nobody cared for
the underflow warnings since some years.

Change-Id: I86bb093987f084c85a7b640a846dfe0aefea9e48
Reviewed-on: https://gerrit.libreoffice.org/63204
Tested-by: Jenkins
Reviewed-by: Jan-Marek Glogowski <glogow@fbihome.de>