Parse a persisted groups array, refusing (returning null) the WHOLE
query rather than silently dropping a group this build cannot read. A
saved filter with an unreadable group is exactly the "matched nothing,
said nothing" defect class #4091 exists to avoid — narrowing it to the
readable groups would change which elements a + union matches without
telling anyone.
Parse a persisted
groupsarray, refusing (returningnull) the WHOLE query rather than silently dropping a group this build cannot read. A saved filter with an unreadable group is exactly the "matched nothing, said nothing" defect class #4091 exists to avoid — narrowing it to the readable groups would change which elements a+union matches without telling anyone.