print the missingval to IO

the missingval itself vas not being printed to io, leading to funny printing during things like docs building with Documenter.

Author: vlandau

src/show.jl

@@ -3,7 +3,7 @@ function DD.show_after(io::IO, mime::MIME"text/plain", A::AbstractRaster)
 
     if missingval(A) !== nothing
         printstyled(io, "with missingval: "; color=:light_black)
-        print(string(missingval(A)), "\n")
+        print(io, string(missingval(A)), "\n")
     end
     if parent(A) isa DiskArrays.AbstractDiskArray 
         if parent(A) isa FileArray