[josm-plugins] global replacement of `Main.map.mapview.getEditLayer()` by `Main.main.getEditLayer()` (avoids NPEs)

git-svn-id: http://svn.openstreetmap.org/applications/editors/josm/plugins@30145 b9d5c4c9-76e1-0310-9c85-f3177eceb1e4