id,node_id,number,title,user,state,locked,assignee,milestone,comments,created_at,updated_at,closed_at,author_association,active_lock_reason,draft,pull_request,body,reactions,performed_via_github_app,state_reason,repo,type
1692597701,I_kwDOAMm_X85k4v3F,7808,Default behaviour of `min_count` wrong with flox,2448579,closed,0,,,0,2023-05-02T15:04:11Z,2023-05-10T02:39:45Z,2023-05-10T02:39:45Z,MEMBER,,,,"### What happened?

```python
with xr.set_options(display_style=""text"", use_flox=False):
    with xr.set_options(use_flox=False):
        display(
            xr.DataArray(
                data=np.array([np.nan, 1, 1, np.nan, 1, 1]),
                dims=""x"",
                coords={""labels"": (""x"", np.array([1, 2, 3, 1, 2, 3]))},
            )
            .groupby(""labels"")
            .sum()
        )

    with xr.set_options(use_flox=True):
        display(
            xr.DataArray(
                data=np.array([np.nan, 1, 1, np.nan, 1, 1]),
                dims=""x"",
                coords={""labels"": (""x"", np.array([1, 2, 3, 1, 2, 3]))},
            )
            .groupby(""labels"")
            .sum()
        )
```

```
# without flox
<xarray.DataArray (labels: 3)>
array([0., 2., 2.])
Coordinates:
  * labels   (labels) int64 1 2 3

# with flox
<xarray.DataArray (labels: 3)>
array([nan,  2.,  2.])
Coordinates:
  * labels   (labels) int64 1 2 3
```

### What did you expect to happen?

The same answer. We should set `min_count=0` when `min_count is None`

### Minimal Complete Verifiable Example

_No response_

### MVCE confirmation

- [ ] Minimal example — the example is as focused as reasonably possible to demonstrate the underlying issue in xarray.
- [ ] Complete example — the example is self-contained, including all data and the text of any traceback.
- [ ] Verifiable example — the example copy & pastes into an IPython prompt or [Binder notebook](https://mybinder.org/v2/gh/pydata/xarray/main?urlpath=lab/tree/doc/examples/blank_template.ipynb), returning the result.
- [ ] New issue — a search of GitHub Issues suggests this is not a duplicate.

### Relevant log output

_No response_

### Anything else we need to know?

_No response_

### Environment

<details>



</details>
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1692612622,PR_kwDOAMm_X85PmMOy,7809,Fix `min_count` behaviour with flox.,2448579,closed,0,,,0,2023-05-02T15:13:17Z,2023-05-10T02:39:45Z,2023-05-10T02:39:43Z,MEMBER,,0,pydata/xarray/pulls/7809,"
- [x] Closes #7808
- [x] Tests added
- [x] User visible changes (including notable bug fixes) are documented in `whats-new.rst`","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/7809/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,,13221727,pull