Fix failing PLC build when building freshly created project that use default libraries blocks. When controller loads libraries according to attibutes in project files (BeremizRoot/Enable_{libname}_Library), use known default if attribute is missing.
<?xml version="1.0" encoding="ISO-8859-1" ?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:xhtml="http://www.w3.org/1999/xhtml">
<xsd:element name="Python">
<xsd:complexType>
<xsd:annotation>
<xsd:documentation>Formatted text according to parts of XHTML 1.1</xsd:documentation>
</xsd:annotation>
<xsd:sequence>
<xsd:any namespace="http://www.w3.org/1999/xhtml" processContents="lax"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
</xsd:schema>