7.0: Documents do not display in Documents UI when Sync Gateway is Running

Documents added to bucket by Sync Gateway do not display in the Documents section of the web UI but they do exist in the bucket as I can query them.

Steps to Reproduce
1. Download & Install Sync Gateway 2.8

2. Add bucket 'default' to cluster

3. Add the following user to the cluster
username: username
password: password
Roles: Bucket --> Application Access --> default

4. Start Sync Gateway from the couchbase-sync-gateway directory:
./bin/sync_gateway examples/basic-couchbase-bucket.json

5. After Sync Gateway has finished started you should see 5 documents in the default bucket (attachment Screen Shot 2020-10-27 at 11.09.56 AM).

6. When trying to view the documents in the Documents section of the UI, notice it states 5 Results for select meta().id from `default`.`_default`.`_default` data order by meta().id limit 10 offset 0 but no documents are displayed (attachment Screen Shot 2020-10-27 at 11.10.14 AM).

7. Create a primary index on the default bucket and execute the following query: SELECT RAW meta().id FROM _default. Note the IDs of the 5 documents are displayed (attachment Screen Shot 2020-10-27 at 11.38.34 AM).

8. Back on the Documents section of the UI, retrieving these documents by ID does work, with the exception of the _sync:heartbeat_timeout:XXXXXXXXXX document (attachment Screen Shot 2020-10-27 at 11.40.08 AM).