Behavior differs between local and non-local properties with no default value

Repro:
```pkl
class A {}
a: A
// result: a {}
local aLocal: A
// error: Missing property value.
```

I would expect `aLocal` to be initialized to the default value of `A` here instead.
This error is thrown during parsing, so it's not even necessary to have `aLocal` in the evaluation path to trigger it.
Also pkl-intellij does not register this as an error, only `pkl eval`.

Reproduce the example with pkl eval and compare its diagnostics with pkl-intellij. Trace the parsing path that reports “Missing property value” for local aLocal and the default-value behavior used for a; done when the local property behaves consistently and both tools report the intended result.

Written by the indexing model from the issue text.