In one case, the code simply checked for isOpen afterwards; refactor
it to use QFile::open's result. In another case, a file was opened
from the resource system, so add a check.
Pick-to: 6.9 6.8
Change-Id: I5f4c22dd5ce678f15c9c1609c4228d50a2b32a1d
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>