Using an undefined variable should result in an error #292
Description
Current behaviour when using an undefined variable is that it evaluates to null.
Arguably, this is never the user's intention.
Rather, this is the case when the variable name was mis-spelled, or forgot to be renamed in an inconsistent refactoring.
Concordion should raise an error in such a case.
<html xmlns:concordion="http://www.concordion.org/2007/concordion">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
</head>
<body>
<p>
When using an undefined variable var
then an <span concordion:assertEquals="#var">error</span> is reported.
</p>
</body>
</html>