Tray icon in xfce-panel Notification Area vanished in 5.0.1
I'm not running a full Xfce desktop, but I am using xfce4-panel 4.12.1 configured with the Notification Area tray that comes with it. (The OS is Debian 9.) With Gitter Desktop 4.x the tray icon worked, though it was blank instead of properly displaying an image. After upgrading to 5.0.1 the tray icon no longer appears when I start Gitter. (Various other programs that use tray icons, such as Telegram, Dropbox and Chrome, continue to work.)
I am guessing that this all uses the freedesktop.org StatusNotifierItem spec. I'm not too familiar with dbus and all of that, but if someone wants to give me debugging tips I'm willing to dig in and see what's on the bus, send and trace messages, and the like.