[{
  "name": "DockerExtension",
  "version": 1.0,
  "handlerManifest": {
    "installCommand":   "bin/docker-extension install",
    "enableCommand":    "scripts/run-in-background.sh enable",
    "uninstallCommand": "bin/docker-extension uninstall",
    "updateCommand":    "bin/docker-extension update",
    "disableCommand":   "bin/docker-extension disable",
    "rebootAfterInstall": false,
    "reportHeartbeat": false,
    "updateMode": "UpdateWithoutInstall"
  }
}]

[{
  "version": 1.0,
  "handlerManifest": {
    "installCommand":   "bin/docker-extension install",
    "enableCommand":    "scripts/run-in-background.sh enable",
    "uninstallCommand": "bin/docker-extension uninstall",
    "updateCommand":    "bin/docker-extension update",
    "disableCommand":   "bin/docker-extension disable",
    "rebootAfterInstall": false,
    "reportHeartbeat": false,
    "updateMode": "UpdateWithoutInstall"
  }
}]

Remove name field from handlermanifest.json
Remove name field from handlermanifest.json

Apparently this field is not required at all.