Issue 922: NPE in Valija code using "use strict,cajita";

In the testbed

<script type="text/javascript">
"use strict,cajita";
var foo;
(function (){
    foo = function () { return 8; };
})();
foo();
</script>

works with the Valija checkbox off, but with it on gives:

java.lang.NullPointerException
    at com.google.caja.parser.quasiliteral.Rewriter.expand(Rewriter.java:108)
    at com.google.caja.parser.quasiliteral.Rule.expandAllTo(Rule.java:193)
    at com.google.caja.parser.quasiliteral.Rule.expandAll(Rule.java:183)
    at com.google.caja.parser.quasiliteral.DefaultValijaRewriter$52.fire(DefaultValijaRewriter.java:1379)

[MarkM, 2009-02-17 21:26:54]

LGTM

[MikeSamuel, 2009-02-17 21:35:48]

@3260