Error out if no author
diff --git a/xslt/epub2i5.xsl b/xslt/epub2i5.xsl
index d6d9aba..70d91a7 100644
--- a/xslt/epub2i5.xsl
+++ b/xslt/epub2i5.xsl
@@ -230,6 +230,10 @@
<xsl:message terminate="yes">ERROR: No title found for ISBN: <xsl:value-of select="$isbn"/></xsl:message>
</xsl:if>
+ <xsl:if test="not(normalize-space($autor))">
+ <xsl:message terminate="yes">ERROR: No author found for ISBN: <xsl:value-of select="$isbn"/></xsl:message>
+ </xsl:if>
+
<idsDoc TEIform="TEI.2" type="text" version="1.0">
<idsHeader TEIform="teiHeader" pattern="text" status="new" type="document" version="1.1">
<fileDesc>