Can't close window; forcing it kills Julia

[mbaz]

This is on OpenBox on X11 and Linux, with Julia 1.5.1, running the "plasma" example.

The window comes up and I can see the visualization. Clicking on the window's "close" button does nothing. Forcing it to close from the window manager, I get this:

• Right-clicking on the taskbar and selecting "close":

julia> plasma()
Window created using X11 API
X connection to :0 broken (explicit kill or server shutdown).
0[~] $

• Sending the window a "close" command via a keyboard shortcut:

julia> plasma()
Window created using X11 API
XIO:  fatal IO error 11 (Resource temporarily unavailable) on X server ":0"
      after 1481 requests (1477 known processed) with 0 events remaining.
0[~] $