Better error message if using e.g. min in zonal

[asinghvi17]

Currently it's a bit inscrutable:

julia> rmin = Rasters.zonal(min, src_srtm; of = zion)
ERROR: MethodError: no method matching min(::Base.SkipMissing{Raster{…}})

Closest candidates are:
  min(::Any, ::Missing)
   @ Base missing.jl:134
  min(::Any, ::Any)
   @ Base operators.jl:490
  min(::Any, ::Any, ::Any, ::Any...)
   @ Base operators.jl:587
  ...

Stacktrace:
  [1] _zonal(f::typeof(min), x::Raster{…}, ::GeoInterface.PolygonTrait, geom::GeoInterface.Wrappers.Polygon{…}; kw::@Kwargs{})
    @ Rasters ~/.julia/dev/Rasters/src/methods/zonal.jl:96
  [2] _zonal(f::Function, x::Raster{…}, ::GeoInterface.PolygonTrait, geom::GeoInterface.Wrappers.Polygon{…})
    @ Rasters ~/.julia/dev/Rasters/src/methods/zonal.jl:92

but maybe we can add a hint in a try-catch block? Not sure if that makes sense to do.

[rafaqz]

Personally that makes total sense to me as an error 😅

Would rather avoid try-catch too

[asinghvi17]

If you don't know what Base.SkipMissing is then it doesn't really make sense I think, but will try and see if there's a nice way to add some info to the error 🤷