When are associative arrays meant to throw a RangeError?

[Andrej Mitrovic]

Well it's probably too late to change this behavior. Both the sample
on the hash page and TDPL itself shows the usage of that trick.

Btw, if you really want Type.init if the key doesn't exist you can use
the get method:
Chunk[] tempVar = chunks.get("CCCC", null) ~ new Chunk();