workaround for a problem if a <select> has no entries and there is no attachement cell

git-svn-id: svn+ssh://svn.gna.org/svn/gnustep/libs/simplewebkit/trunk@36570 72102866-910b-0410-8b05-ffd578937521
added code to SWKBrowser and fixed connections in NIB file to implement GUI side of Issue 437

git-svn-id: svn+ssh://svn.gna.org/svn/gnustep/libs/simplewebkit/trunk@36571 72102866-910b-0410-8b05-ffd578937521