IDE: Workaround some reported WxPython/MacOS problems.

SetSelection should be used instead of SetStringSelection , and FindString must use case_sensitive=True

<?xml version='1.0' encoding='utf-8'?>
<ModbusServerNode xmlns:xsd="http://www.w3.org/2001/XMLSchema" Local_Port_Number="1502" Local_IP_Address="127.0.0.1"/>