When re-allocating the sparse array data, make sure to initialize the free list
correctly. Previously this was only done for the first allocation.
Test cases uses an object literal, as that's a reliable way to ensure
a sparse array is created.
Task-number: QTBUG-37892
Change-Id: Ib38cfce50104904af0c980f022c9dbb7461ae5f8
Reviewed-by: Lars Knoll <lars.knoll@digia.com>