fix #8582 - synchronize Main.removeLayer()

git-svn-id: http://josm.openstreetmap.de/svn/trunk@5896 0c6e7542-c601-0410-84e7-c038aed88b3b
see #8582 - Use Main.removeLayer() everywhere

git-svn-id: http://josm.openstreetmap.de/svn/trunk@5897 0c6e7542-c601-0410-84e7-c038aed88b3b
Merge branch 'master' into mirror