tests/modbus/modbus_0@modbus/ModbusTCPserver_0@ModbusTCPserver/HoldingRegs@MemoryArea/confnode.xml
Attempt to workaround problem reported about empty plc.xml after unrelated crash. Now, if etree model is corrupted in a way tostring() would generate an empty string, exception prevents saving.
<?xml version='1.0' encoding='utf-8'?>
<MemoryArea xmlns:xsd="http://www.w3.org/2001/XMLSchema" MemoryAreaType="03 - Holding Registers" Nr_of_Channels="1"/>