... & fix build.
When fixing tests I noticed a bug exposed by the new VisitFrequency metrics. MergeDataTables will only iterate over the first table when merging tables, which means if there are tables that exist in table2 only, they won't get added.
Would it be possible adding some unit tests or so?
👍 can add unit tests
@diosmosis looks like you forgot to add the unit tests in https://github.com/matomo-org/matomo/pull/15294/commits/1c83ed2ed1f8b5a6b89987aa70b7a579f83f3b3d ?