fix bug with TextViewer instance in debug mode, appears after transferring new program on PLC
TextViewer isn't able to display debug values, so calling for this class SubscribeAllDataConsumers method causes error
<?xml version='1.0' encoding='utf-8'?>
<PyFile xmlns:xhtml="http://www.w3.org/1999/xhtml" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<variables>
<variable name="SomeVarName" type="DINT"/>
<variable name="Grumpf" type="STRING"/>
</variables>
<globals>
<xhtml:p><![CDATA[
print "All python PLC globals variables :", PLCGlobalsDesc
print "Current extention name :", __ext_name__
]]></xhtml:p>
</globals>
<init>
<xhtml:p><![CDATA[
]]></xhtml:p>
</init>
<cleanup>
<xhtml:p><![CDATA[
]]></xhtml:p>
</cleanup>
<start>
<xhtml:p><![CDATA[
]]></xhtml:p>
</start>
<stop>
<xhtml:p><![CDATA[
]]></xhtml:p>
</stop>
</PyFile>