encapsulation for shadow tiddlers

[FND]

Fixed in changeset:6365

[SaqImtiaz]

I have some concerns about the way this has been implemented, in particular that getShadowTiddlerText returns a 'empty' string - that is "" - when the shadow tiddler does not exist. This means that if I call getShadowTiddlerText and get a "" value, I cannot distinguish between a blank shadow tiddler and a non-existent one. Would be more beneficial to return undefined.

Note that whilst it is possible to call isShadowTiddler to see if the tiddler exists, this is unnecessarily complex given that getShadowTiddlerText can just return undefined.

Also note that we have a precedence with the behaviour of TiddlyWiki.prototype.getTiddlerText and getRecursiveTiddlerText. Both accept a second "defaultText" parameter to return when the tiddler does not exist and when called without this parameter return undefined.

[MartinBudden]

The current behaviour simplifies some processing. In the cases where the user requires to know if the shadow tiddler exists there is a function that can be called.