## Steps to reproduce:

- create 2 separate repos
- Top right: Repository: path dropdown
  - Select the other repository

## Expected result

I expect the UI to switch over to the other repo.

## Actual result

```
Internal Server Error
HttpExceptionRequest Request {
  host                 = "127.0.0.1"
  port                 = 52482
  secure               = False
  requestHeaders       = [("Accept-Encoding","")]
  path                 = "/"
  queryString          = "?auth=REDACTED"
  method               = "HEAD"
  proxy                = Nothing
  rawBody              = False
  redirectCount        = 10
  responseTimeout      = ResponseTimeoutDefault
  requestVersion       = HTTP/1.1
  proxySecureMode      = ProxySecureWithConnect
}
 (ConnectionFailure Network.Socket.connect: <socket: 51>: does not exist (Connection refused))
```

## Context

```
git-annex version: 8.20210127
build flags: Assistant Webapp Pairing FsEvents TorrentParser MagicMime Feeds Testsuite S3 WebDAV
dependency versions: aws-0.22 bloomfilter-2.0.1.0 cryptonite-0.28 DAV-1.3.4 feed-1.3.0.1 ghc-8.10.3 http-client-0.7.4 persistent-sqlite-2.11.0.0 torrent-10000.1.1 uuid-1.3.13 yesod-1.6.1.0
key/value backends: SHA256E SHA256 SHA512E SHA512 SHA224E SHA224 SHA384E SHA384 SHA3_256E SHA3_256 SHA3_512E SHA3_512 SHA3_224E SHA3_224 SHA3_384E SHA3_384 SKEIN256E SKEIN256 SKEIN512E SKEIN512 BLAKE2B256E BLAKE2B256 BLAKE2B512E BLAKE2B512 BLAKE2B160E BLAKE2B160 BLAKE2B224E BLAKE2B224 BLAKE2B384E BLAKE2B384 BLAKE2BP512E BLAKE2BP512 BLAKE2S256E BLAKE2S256 BLAKE2S160E BLAKE2S160 BLAKE2S224E BLAKE2S224 BLAKE2SP256E BLAKE2SP256 BLAKE2SP224E BLAKE2SP224 SHA1E SHA1 MD5E MD5 WORM URL X*
remote types: git gcrypt p2p S3 bup directory rsync web bittorrent webdav adb tahoe glacier ddar git-lfs httpalso borg hook external
operating system: darwin x86_64
supported repository versions: 8
upgrade supported from repository versions: 0 1 2 3 4 5 6 7
local repository version: 8
```

This is macOS 11.2.1 (Big Sur), installed via `brew install git-annex`. I've tried the same behaviour on 2 separate macs, same error both times. It seems like the switching in the web UI is a bit tricky. I've also tried a few browsers (Safari, Chrome) and my dev browser without any ad blocking. It seems like there's an HTTP request to `/config/repository/switchto/...` which returns a 500.

## Workaround

It seems that if I stop the webapp, and start it again, it has actually switched repos. So it's a bit inconvenient, but usable nonetheless.

## Thanks

I've just started the missing of moving from nextcloud to git-annex after the second random deletion of data by nextcloud. I'm deeply grateful to the authors for giving me the confidence of git to manage my files. Wonderful.
