Fix mapping for simple array types (i.e. string[])

When using a mapping of `string[]` in a namespaced class, it attempted to construct an object using `new \namespace\string ($value)` which is not valid.

I've also added a test case to test for this functionality.
I don't understand why you add this here. We're having a flat (non-array simple) value. Removing that line does also not break the tests.