No citation number causes weird preview output

gistfile1.txt

<?xml version="1.0" encoding="utf-8"?>
<!-- Author Date Style

31/05/2018 New: Original version [RN]
06/06/2018 Fix: Syntax error in author-short macros fixed [RN]
11/06/2018 Mod: Citation number removed [RN]

-->
<style xmlns="http://purl.org/net/xbiblio/csl" class="in-text" version="1.0" demote-non-dropping-particle="sort-only" default-locale="en-US" page-range-format="expanded">

	<!-- Information about style -->
	<info>
		<title>Helios Author Date</title>
		<id>http://www.zotero.org/styles/helios-author-date</id>
		<link href="http://www.zotero.org/styles/vancouver" rel="self"/>
		<link href="http://www.nlm.nih.gov/bsd/uniform_requirements.html" rel="documentation"/>
		<author>
			<name>Susan Thorp</name> 
			<email>susan.thorp@heliosmedcomms.com</email>
		</author>
		<contributor>
			<name>Rob Nicholson</name>
			<email>rob.nicholson@heliosmedcomms.com</email>
		</contributor>
		<category citation-format="author-date"/>
		<category field="medicine"/>
		<summary>This is the standard Helios author date style for citations.</summary>
		<updated>2018-06-11T08:52:03+00:00</updated>
		<rights license="http://creativecommons.org/licenses/by-sa/3.0/">This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 License</rights>
	</info>

  	<!-- Author: render the author string -->
	<macro name="author">
		<names variable="author">
			<name sort-separator=" " initialize-with="" name-as-sort-order="all" delimiter=", " delimiter-precedes-last="always"/>
			<label form="short" prefix=", "/>
			<substitute><text macro="editor"/></substitute>
		</names>
	</macro>

	<!-- Author-Short: render the short author string -->
	<macro name="author-short">
		<names variable="author">
			<name form="short" and="text" delimiter=", " initialize-with=""/>
			<substitute><text macro="editor"/></substitute>
		</names>	
	</macro>

	<!-- Editor: render list of editors -->
	<macro name="editor">
		<names variable="editor">
			<name name-as-sort-order="all" sort-separator=" " initialize-with=""/>
			<label form="long" prefix=", " suffix=". " />
		 </names>
	</macro>
  
	<!-- Issued: get issued date or accessed if not present and website -->
	<macro name="issued">
		<choose>
			<if variable="issued">
				<date variable="issued"><date-part name="year"/></date>
			</if>
			<else-if variable="accessed">
				<choose>
					<if type="webpage">
						<date variable="accessed"><date-part name="year"/></date>
					</if>
					<else>
						<text term="no date" form="short"/>
					</else>
				</choose>
			</else-if>
			<else>
				<text term="no date" form="short"/>
			</else>
		</choose>
	</macro>

	<!-- Publisher: <publisher-place>: <publisher> -->
	<macro name="publisher">
		<group delimiter=": ">
			<text variable="publisher-place"/>
			<text variable="publisher"/>
		</group>
	</macro>
  
	<!-- article-journal -->
	<macro name="render-article-journal">
		<text macro="author" suffix=". "/>
		<date variable="issued" suffix=". "><date-part name="year"/></date>
		<text variable="title" suffix=". "/>
		<group delimiter=";" suffix=". ">
			<text variable="container-title" form="short" strip-periods="true"/>
			<choose>
				<if variable="page">
					<group delimiter=":">
						<text variable="volume"/>
						<text variable="page"/>
					</group>
				</if>
				<else-if variable="DOI">
					<group suffix=" [Epub ahead of print]">
						<text variable="DOI" prefix="doi "/>
						<date variable="issued" prefix=": ">
							<date-part name="month" form="short" strip-periods="true" suffix=" "/>
							<date-part name="day"/>
						</date>
					</group>
				</else-if>
			</choose>
		</group>
	</macro>

	<!-- chapter (book section) -->
	<macro name="render-chapter">
		<text macro="author" suffix=". "/>
		<date variable="issued" suffix=". "><date-part name="year"/></date>
		<text variable="title" suffix=". "/>
		<text term="in" suffix=": " text-case="capitalize-first"/>
		<text macro="editor"/>
		<group suffix=". ">
			<text variable="container-title"/>
			<text variable="edition" prefix=" (" suffix=")"/>
		</group>
		<group delimiter=" " suffix=".">
			<text macro="publisher"/>
			<text variable="page" prefix=" p. "/>
		</group>
	</macro>

	<!-- book -->
	<macro name="render-book">
		<text macro="author" suffix=". "/>
		<date variable="issued" suffix=". "><date-part name="year"/></date>
		<group delimiter=" " suffix=". ">
			<text variable="title"/>
			<text variable="edition" prefix="(" suffix=")"/>
		</group>
		<text macro="publisher" suffix="."/>
	</macro>

	<!-- webpage -->
	<macro name="render-webpage">
		<text macro="author" suffix=". "/>
		<date variable="issued" suffix=". ">
			<date-part name="day"/>
			<date-part name="month" prefix=" "/>
			<date-part name="year" prefix=" "/>
		</date>
		<text variable="title" suffix=". "/>
		<choose>
			<if variable="URL">
				<group delimiter=" " suffix=".">
					<text variable="URL" prefix="Available from: "/>
					<group delimiter=" " prefix="(" suffix=").">
						<text term="accessed" text-case="capitalize-first"/>
						<date variable="accessed">
							<date-part name="day"/>
							<date-part name="month" prefix=" "/>
							<date-part name="year" prefix=" "/>
						</date>
					</group>
				</group>
			</if>
		</choose>
	</macro>

	<!-- report -->
	<macro name="render-report">
		<text macro="author" suffix=". "/>
		<date variable="issued" suffix=". "><date-part name="year"/></date>
		<group delimiter=" " suffix=".">
			<text variable="title"/>
			<text variable="page"/>
		</group>
	</macro>
	
	<!-- Defines the layout of the citation -->
	<citation et-al-min="3" et-al-use-first="1" disambiguate-add-year-suffix="true" disambiguate-add-names="true" collapse="year">
		<sort>
			<key macro="issued"/>
			<key macro="author"/>
		</sort>
		<layout prefix="(" suffix=")" delimiter="; ">
			<group delimiter=" ">
				<text macro="author-short"/>
				<text macro="issued"/>
			</group>
		</layout>
	</citation>
  
	<!-- Defines the layout of the bibliography -->
	<bibliography et-al-min="7" et-al-use-first="3" second-field-align="flush">
		<layout>
			<!-- <text variable="citation-number" suffix=". "/> -->
			<!-- Uncomment this line to include the type for debugging. Comment it back out when finished as it fails validation -->
			<!-- <text variable="type" prefix="{" suffix="} "/> -->
			<choose>
				<if 		type="article-journal" 	match="any"><text macro="render-article-journal"/></if>
				<else-if 	type="chapter" 			match="any"><text macro="render-chapter"/></else-if>
				<else-if 	type="webpage" 			match="any"><text macro="render-webpage"/></else-if>
				<else-if 	type="book" 			match="any"><text macro="render-book"/></else-if>
				<else-if 	type="report" 			match="any"><text macro="render-report"/></else-if>
				<else><text value="Type not supported: "/><text variable="title"/></else>
			</choose>
		</layout>
	</bibliography>

</style>