XPATH Issue in Real Excel Templates

Dears Community

 We are working on an real Excel Template.

 The structure of the XML Input may vary: So for example either the ListOfContact or the ListOfAccount have exactly one child element.

 As it seems the “for each” tag is having problems if it references an not existing tag? The template viewer produce always an FO Formating Failed exception.

I tried several ways to handle this issue, for example with an “if statement”, but unfortunately I got the same error.

<xsl:if test="//ListOfContact/Contact"><xsl:for-each-group select="//ListOfContact/Contact/ListOfMobiPolicyContact/MobiPolicyContact[MOBIPremiumCharge!='']" group-by="./AssetId">

Is there a way to handle this with bi publisher xpath syntax?