This method takes a pointer+size pair, but begins reading through the pointer
without first checking the size parameter. Fixed by checking the size parameter.
A new test case is added with an empty binary json file. Although the test does
not fail under normal conditions, the problem can be detected using valgrind or
AddressSanitizer.
Task-number: QTBUG-61969
Change-Id: Ie91cc9a56dbc3c676472c614d4e633d7721b8481
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>