fix debug button and variable tree generate for actions and transitions in POU instance variable panel
for 'None' type instances(Python POU's, Native, SVGUI, user-defined pou's, etc.) debug button will be disabled. If action or transition instances have opened in instance variable panel,variables from main POU will be loaded. When user press debug button on variable instance in action or transition, instance path to main POU will be used, because all variables of action or transition in instance variable tree belong to main POU.

<?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>