Incomplete data is not supported

[bjoern-tantau]

When the tss is trying to read a non-existent property an uncaught TypeError is thrown.

var xml = '<h1>Foo</h1>';
var tss = 'h1 { repeat: data(headlines); content: iteration(); }';
var template = new Tranjsform.Builder(xml, tss);
template.output();

> tranjsform.js:784 Uncaught TypeError: Cannot read property 'headlines' of undefined
>     at Tranjsform.DataFunction.observe (tranjsform.js:784)
>     at Tranjsform.DataFunction.data (tranjsform.js:757)
>     at Tranjsform.Hook.parseValue (tranjsform.js:449)
>     at Tranjsform.Hook.run (tranjsform.js:418)
>     at Tranjsform.Template.processHooks (tranjsform.js:197)
>     at Tranjsform.Template.output (tranjsform.js:205)
>     at Tranjsform.Builder.output (tranjsform.js:38)
>     at <anonymous>:1:10

template.output({});

> tranjsform.js:737 Uncaught TypeError: Cannot read property '0' of undefined
>     at Tranjsform.DataFunction.bind (tranjsform.js:737)
>     at Tranjsform.Property.Repeat.run (tranjsform.js:692)
>     at Tranjsform.Hook.callProperty (tranjsform.js:425)
>     at Tranjsform.Hook.run (tranjsform.js:418)
>     at Tranjsform.Template.processHooks (tranjsform.js:197)
>     at Tranjsform.Template.output (tranjsform.js:205)
>     at Tranjsform.Builder.output (tranjsform.js:38)
>     at <anonymous>:1:10