Fix sorting and deleting sub blocks in order tab.

Release 19.0.0-alpha.19

Release 18.30.1

Release 17.23.0

Release @plone/slate 19.0.0-alpha.9

Release 18.30.0

Release @plone/types 1.5.1

Release @plone/slate 18.8.0

Release 19.0.0-alpha.18

Fix dragging invalid blocktypes in order tab