Xlib's default protocol-error handler calls exit() on any async X error,
so a tray race (tray manager window dying between find and dock, XMoveWindow
on a popup the WM already destroyed) would take the whole UI process down.
Install process-global logging no-op handlers via XSetErrorHandler/
XSetIOErrorHandler after every XOpenDisplay. Since the handler slot is
process-global and GDK init can clobber it, additionally wrap the popup
code's raw Xlib calls on GDK's Display in gdk_x11_display_error_trap_push/
pop_ignored, which is independent of the global handler.
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