Groovy Templates should treat missing variables as null rather than throw MissingPropertyException's

See Testing for nonexistent properties in groovy templates from the Groovy User list.

SimpleTemplateEngine should evaluate ${notAlwaysAvailable == null} to true if the variable is missing from the template binding. Instead it throws: Exception in thread "main" groovy.lang.MissingPropertyException: No such property: notAlwaysAvailable for class: SimpleTemplateScript4.

An exception in this case is not very useful, and is inconsistent with most other template implementations such as: the Java Unified Expression Language; the Spring Expression Language; FreeMarker; Velocity; and Ant, Maven and Spring property substitution.

The binding.variables.contains("notAlwaysAvailable") workaround is overly verbose, as is having to implement your own binding or template engine.