Related: #i124096# correct LayoutManager::m_xDockingAreaAcceptor clear...

on disposing

(cherry picked from commit 50b10da7434d774ac463c148bbaeb051d2b3a22d)

Conflicts:
	framework/source/layoutmanager/layoutmanager.cxx

Change-Id: I51fe74698f00fadba9afaeb0f8e9f66b85f208cb