LXQT Panel shown as windows after Settings window open

[Ryan Reamsbottom]

When you open the LXQT configuration for a panel, Plank will open a dock item for LXQT Panel. This is fine. However, when you close the configuration, Plank retains the dock item for LXQT Panel, in my case it has two items in it both named "LXQt Panel" since I have two panels.

Relevant information from xprop for configuration window:

WM_CLASS(STRING) = "lxqt-panel", "lxqt-panel"
WM_NAME(STRING) = "Configure Panel"

xprop information for the panels themselves:

WM_NAME(STRING) = "LXQt Panel"
WM_CLASS(STRING) = "lxqt-panel", "lxqt-panel"

Expected Behavior:
Plank opens dock item for configuration, closes it when configuration closes.

Actual behavior:
Plank opens item for configuration, retains item after configuration is closed, listing the panel(s)

Workaround:
After finishing configuring the panel, open Plank settings -> Behavior -> uncheck Show Unpinned, and then recheck it. LXQt panel item disappears, so Plank is seeing the panel as a panel, it's just getting confused when the Configuration window is open.

$ plank --version
0.11.4
- Debian testing "buster"
- Linux hostname 4.17.0-3-amd64 #1 SMP Debian 4.17.17-1 (2018-08-18) x86_64 GNU/Linux
- LXQt with Xfwm4, openbox displays the same behavior