Release 0.19.4

# History

## 0.19.4

Install/update via the bootstrap script:

```shell
wget https://raw.githubusercontent.com/dokku/dokku/v0.19.4/bootstrap.sh
sudo DOKKU_TAG=v0.19.4 bash bootstrap.sh
```

### Bug Fixes

- #3755: @dean1012 Warn if key_file is missing on install but do not exit

docs/assets/versions.json

@@ -16,6 +16,6 @@
     "0.16.4",
     "0.17.9",
     "0.18.5",
-    "0.19.3"
+    "0.19.4"
   ]
 }