possible dtype overflow when doing `expressions`

The remote sensing index creation needs float as dtype that goes into negative and such, if by any chance the expression keeps dtype from source, this can cause issues. From what I saw I get invalid output from (B03-B08)/(B03+B08) over land. Tho I have been known to be wrong before...so

          ndwi:
            roles:
              - virtual
              - data
              - index
            href: "#/assets/ndwi"
            vrt:hrefs:
              - key: B03
                href: "#/assets/green"
              - key: B08
                href: "#/assets/nir"
            title: "Normalized Difference Water Index"
            vrt:algorithm: "band_arithmetic"
            vrt:algorithm_opts:
              expression: (B03-B08)/(B03+B08)
              rescale:
                - - -1
                  - 1