The compressor tried to increase the number of rows between None and 8118358

Nobody has claimed this yet.

**Describe the bug**
On some rooms I got a warning with understandable description, but with weird values, like this:
```
[2022-03-04T13:33:16Z WARN synapse_auto_compressor::manager] The compressor tried to increase the number of rows in !aQCReTFThhdPggxxxx:matrix.org between None and 1255815. Skipping...
[2022-03-04T13:33:25Z WARN synapse_auto_compressor::manager] The compressor tried to increase the number of rows in !tEQSCZnuDbXmbZxxxx:t2bot.io between None and 4685024. Skipping...
[2022-03-04T13:33:27Z WARN synapse_auto_compressor::manager] The compressor tried to increase the number of rows in !myvvLiHwOQQAvqxxxx:t2bot.io between None and 14432. Skipping...
```

Why the first value is "None" instead of some numeric value?

And can you explain in more detail what this warning means and is there any workaround to force compress such rooms?

Start at the warning emitted by synapse_auto_compressor::manager and trace how the two row-count values are obtained for affected rooms. Reproduce or inspect the reported None value and determine what the warning means and whether compression can be forced. Done means the cause and any supported workaround are documented, with a fix if the value is erroneous.

Written by the indexing model from the issue text.