Missing Fields Export Error

ExportCollection_Zotero.rdf

<rdf:RDF
 xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
 xmlns:z="http://www.zotero.org/namespaces/export#"
 xmlns:dcterms="http://purl.org/dc/terms/"
 xmlns:dc="http://purl.org/dc/elements/1.1/"
 xmlns:bib="http://purl.org/net/biblio#"
 xmlns:foaf="http://xmlns.com/foaf/0.1/"
 xmlns:prism="http://prismstandard.org/namespaces/1.2/basic/">
    <bib:Book rdf:about="#item_614">
        <z:itemType>book</z:itemType>
        <dcterms:isPartOf>
           <bib:Series><dc:title>1</dc:title></bib:Series>
        </dcterms:isPartOf>
        <bib:authors>
            <rdf:Seq>
                <rdf:li>
                    <foaf:Person>
                        <foaf:surname>last</foaf:surname>
                        <foaf:givenname>first</foaf:givenname>
                    </foaf:Person>
                </rdf:li>
            </rdf:Seq>
        </bib:authors>
        <prism:volume>1</prism:volume>
        <dc:date>2015</dc:date>
        <dc:title>test title</dc:title>
    </bib:Book>
</rdf:RDF>

ExportColllection_Better_BibLatex.bib

@book{zotero-null-614,
  timestamp = {2015-09-11 13:41:53}
}

ExportColllection_BibLatex.bib

@book{last_test_2015,
	title = {test title},
	volume = {1},
	series = {1},
	author = {last, first},
	date = {2015}
}