Log Message:
xfce4-panel: update to 4.16.4

Change log:

4.16.4 (2022-04-16)
======
- Update copyright year and standardize formatting
- Update and sort author list by name
- panel: Fix regression "intellihide does not hide when leaving \ 
slowly" (#388)
- panel: Fix regression "'Span Monitor' has no effect" (#405)
- panel: Keep a reference on item during drag and drop
- Fix `core.UndefinedBinaryOperatorResult` warning from `scan-build` (#142)
- panel: Fix broken drag and drop between panels (#561)
- panel: Disconnect from screen signals when window is destroyed
- systray: Do not connect to proxy signal if async method failed
- panel: Mitigate a memory leak when removing items (!46)
- windowmenu: Emit "deactivate" signal when hiding the menu (#22, !68)
- systray: Fix wrong sanity check
- systray: Properly initialize systray item
- systray: Trust the status to update the attention icon (#392, !64)
- Fixed some window buttons not appearing in the panel (#188, !66)
- launcher: Only activate under mouse (Fixes #519)
- libxfce4panel: Review memory management for context menu (#452, !46)
- actions: Block panel autohide (Fixes #431, !62)
- launcher: Clear action menu when destroyed (Fixes #540, !61)
- Translation Updates:
  Arabic, Armenian (Armenia), Catalan, Malay, Occitan (post 1500),
  Polish, Romanian, Russian, Slovenian, Spanish, Swedish, Thai