Fix flickering in debug panel

This flickering made debug panel unusable, because most of the time
panel was white. This problem effects wxPython with GTK3+ backend
(at least on GNU/Linux systems).

Removed code IIUC draws box with content of moved debug variable, I
don't see any effect of it neither on GNU/Linux nor on Windows. It
should be safe to remove.

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<?xml version='1.0' encoding='utf-8'?>

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<ModbusServerNode xmlns:xsd="http://www.w3.org/2001/XMLSchema" Local_Port_Number="1502" Local_IP_Address="127.0.0.1"/>