pydata__xarray-4075

[bug] when passing boolean weights to weighted mean

Verdict: the fix is stated in the issue (Tier A).

We'll need to convert it to int or float: ```python xr.dot(dta.notnull(), wgt * 1) ```

The text states the fix: “We'll need to convert it to int or float: ```python xr.dot(dta.notnull(), wgt * 1) ```”