null Quality defect

An error occurred while processing the template.
The following has evaluated to null or missing:
==> dateTool  [in template "10155#10195#22629" at line 7, column 33]

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Tip: If the failing expression is known to be legally refer to something that's sometimes null or missing, either specify a default value like myOptionalVar!myDefault, or use <#if myOptionalVar??>when-present<#else>when-missing</#if>. (These only cover the last step of the expression; to cover the whole expression, use parenthesis: (myOptionalVar.foo)!myDefault, (myOptionalVar.foo)??
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FTL stack trace ("~" means nesting-related):
	- Failed at: #assign publish_date = dateTool.toDat...  [in template "10155#10195#22629" at line 7, column 9]
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1<article class="article-details"> 
2    <h2>${title.getData()}</h2> 
3    <div class="article-image"> 
4        <img src="${bigimg.getData()}" alt="${title.getData()}" /> 
5    </div> 
6      <#if datebool?? && getterUtil.getBoolean(datebool.getData()) > 
7        <#assign publish_date = dateTool.toDate('EEE, dd MMM yyyy hh:mm:ss Z', reserved-article-display-date.getData(), locale) > 
8        <date>${dateTool.format("yyyy. MMMM d, EEEE", publish_date, locale)}</date> 
9      </#if> 
10    <p class="lead">${lead.getData()}</p> 
11    ${text.getData()} 
12</article>