Freemarker exception for comment form

2012-08-07 15:15:24,624 ERROR [qtp813385475-2949] [runtime] Expression user.fullName is undefined on line 12, column 81 in feature/comments/commentForm.ftl.

Expression user.fullName is undefined on line 12, column 81 in feature/comments/commentForm.ftl.
The problematic instruction:
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==> ${user.fullName?html} [on line 12, column 79 in feature/comments/commentForm.ftl]
in user-directive ui.displayUserGravatar [on line 12, column 5 in feature/comments/commentForm.ftl]
in user-directive ww.form [on line 1, column 1 in feature/comments/commentForm.ftl]
in include "/feature/comments/commentForm.ftl" [on line 795, column 13 in lib/components.ftl]
in user-directive cp.displayComments [on line 2, column 1 in URLTemplate]
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Java backtrace for programmers:
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freemarker.core.InvalidReferenceException: Expression user.fullName is undefined on line 12, column 81 in feature/comments/commentForm.ftl.
at freemarker.core.TemplateObject.assertNonNull(TemplateObject.java:124)
at freemarker.core.Expression.getStringValue(Expression.java:118)
at freemarker.core.Expression.getStringValue(Expression.java:93)
at freemarker.core.StringBuiltins$StringBuiltIn._getAsTemplateModel(StringBuiltins.java:71)
at freemarker.core.Expression.getAsTemplateModel(Expression.java:89)
at freemarker.core.Expression.getStringValue(Expression.java:93)
at freemarker.core.DollarVariable.accept(DollarVariable.java:76)
at freemarker.core.Environment.visit(Environment.java:210)