fix #9201 - fix remote control usage examples for handlers with several commands + typo

git-svn-id: http://josm.openstreetmap.de/svn/trunk@6332 0c6e7542-c601-0410-84e7-c038aed88b3b
fix #9189 - NPE when deleting data layer + additional usage of `Main.isDisplayingMapView()`

git-svn-id: http://josm.openstreetmap.de/svn/trunk@6333 0c6e7542-c601-0410-84e7-c038aed88b3b