Stacktrace when viewing 'About FAQ' document

• install FAQ through Essentials.
• navigate to document 'About FAQ'
• click View | Hippo10

a stacktrace is shown:

[INFO] [talledLocalContainer] Java stack trace (for programmers):
[INFO] [talledLocalContainer] ----
[INFO] [talledLocalContainer] freemarker.core.InvalidReferenceException: [... Exception message was already printed; see it above ...]
[INFO] [talledLocalContainer] at freemarker.core.InvalidReferenceException.getInstance(InvalidReferenceException.java:116)
[INFO] [talledLocalContainer] at freemarker.core.EvalUtil.coerceModelToString(EvalUtil.java:346)
[INFO] [talledLocalContainer] at freemarker.core.Expression.evalAndCoerceToString(Expression.java:82)
[INFO] [talledLocalContainer] at freemarker.core.BuiltInForString._eval(BuiltInForString.java:26)
[INFO] [talledLocalContainer] at freemarker.core.Expression.eval(Expression.java:78)
[INFO] [talledLocalContainer] at freemarker.core.Expression.evalAndCoerceToString(Expression.java:82)
[INFO] [talledLocalContainer] at freemarker.core.DollarVariable.accept(DollarVariable.java:40)
[INFO] [talledLocalContainer] at freemarker.core.Environment.visit(Environment.java:312)
[INFO] [talledLocalContainer] at freemarker.core.MixedContent.accept(MixedContent.java:62)
[INFO] [talledLocalContainer] at freemarker.core.Environment.visitByHiddingParent(Environment.java:333)
[INFO] [talledLocalContainer] at freemarker.core.ConditionalBlock.accept(ConditionalBlock.java:48)
[INFO] [talledLocalContainer] at freemarker.core.Environment.visit(Environment.java:312)
[INFO] [talledLocalContainer] at freemarker.core.MixedContent.accept(MixedContent.java:62)
[INFO] [talledLocalContainer] at freemarker.core.Environment.visit(Environment.java:312)
[INFO] [talledLocalContainer] at freemarker.core.Environment.process(Environment.java:290)
[WARNING] [talledLocalContainer] 16:36:42 WARN The following has evaluated to null or missing:
[INFO] [talledLocalContainer] at freemarker.template.Template.process(Template.java:312)
[INFO] [talledLocalContainer] ==> document.question [in template "webfile:/freemarker/hippo10/faq-main.ftl" at line 7, column 7]
[INFO] [talledLocalContainer] at freemarker.ext.servlet.FreemarkerServlet.process(FreemarkerServlet.java:778)
[INFO] [talledLocalContainer] at freemarker.ext.servlet.FreemarkerServlet.doGet(FreemarkerServlet.java:695)
[INFO] [talledLocalContainer] at org.hippoecm.hst.servlet.HstFreemarkerServlet.doGet(HstFreemarkerServlet.java:134)
[INFO] [talledLocalContainer] at javax.servlet.http.HttpServlet.service(HttpServlet.java:622)
[INFO] [talledLocalContainer] at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
[INFO] [talledLocalContainer] at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291)
[INFO] [talledLocalContainer]
[INFO] [talledLocalContainer] at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
[INFO] [talledLocalContainer] ----
[INFO] [talledLocalContainer] at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:721)
[INFO] [talledLocalContainer] Tip: It's the step after the last dot that caused this error, not those before it.
[INFO] [talledLocalContainer] at org.apache.catalina.core.ApplicationDispatcher.doInclude(ApplicationDispatcher.java:584)
[INFO] [talledLocalContainer] ----
[INFO] [talledLocalContainer] at org.apache.catalina.core.ApplicationDispatcher.include(ApplicationDispatcher.java:523)