use :noArg for get commands

git-svn-id: svn://svn.code.sf.net/p/fhem/code/trunk@3640 2b470e98-0d58-463d-a4d8-8e2adae1ed80

fhem/FHEM/31_LightScene.pm

@@ -446,7 +446,7 @@ LightScene_Get($@)
     return $ret;
   }
 
-  return "Unknown argument $cmd, choose one of html scenes scene";
+  return "Unknown argument $cmd, choose one of html:noArg scenes:noArg scene:".join(",", sort keys %{$hash->{SCENES}})};
 }
 
 1;