Fix crash when Android Style is set more than once.

Load again JSON document is it was freed.

Task-number: QTBUG-43111
Change-Id: I22f1de221371b49fec8b3d66ad5f0bd2af9656fe
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@theqtcompany.com>