fix schema for structs

Author: Pietro Vertechi

src/tables.jl

@@ -6,4 +6,4 @@ Tables.columnaccess(::Type{<:StructVector}) = true
 Tables.rows(s::StructVector) = s
 Tables.columns(s::StructVector) = fieldarrays(s)
 
-Tables.schema(s::StructVector) = Tables.Schema(eltype(s))
+Tables.schema(s::StructVector) = Tables.Schema(staticschema(eltype(s)))