fix #9068 - Warn about empty key/values on upload tags



git-svn-id: http://josm.openstreetmap.de/svn/trunk@6309 0c6e7542-c601-0410-84e7-c038aed88b3b
Sonar/FindBugs - Nested blocks of code should not be left empty

git-svn-id: http://josm.openstreetmap.de/svn/trunk@6310 0c6e7542-c601-0410-84e7-c038aed88b3b