fix problem with clearing non-empty location field after changing type of config variable
introduced by cd9db17 ("clear variable location cell in variable
panel, if variable class or type changed").
Closes #26
<?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="PyVar0" type="DINT"/>
<variable name="PyVar1" type="DINT"/>
</variables>
<globals>
<xhtml:p><![CDATA[]]></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>