When the partition table is present **but** empty, the existing code would output fields followed by a `,` , on the assumption that the list of partitions would follow. But if the list of partitions is empty, it is skipped, leading to output like this:
```
{
"partitiontable": {
"label":"gpt",
"id":"1F9E80D9-DD78-024F-94A3-B61EC82B18C8",
"device":"/dev/sdb",
"unit":"sectors",
"firstlba":2048,
"lastlba":30949342,
"sectorsize":512,
}
}
```
Note the `512,` on the *sectorsize* line.
This is invalid JSON for some parsers, which choke on it.
Avoid this, by checking when outputting the last separator: if there's no table, or there is a table but it is empty, then just put a newline, otherwise use the old path of comma-newline and assume there's going to be a list of partitions after.
bc743b355c