The serialization code neglected to check against null. Sinze zones
are saved either by IANA ID or in our special OffsetFromUtc format,
representing an invalid zone by a string that cannot possibly be a
valid IANA ID will do.
Fixes: QTBUG-86019
Pick-to: 5.15
Pick-to: 5.12
Change-Id: I6882026403d00f8b254aab34c645f1cf8f9fcc2d
Reviewed-by: Taylor Braun-Jones <taylor@braun-jones.org>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
14f3f419b0