`mortar([Block(1)[1:2], Block(2)[1:2]])[Block(1)]` has type `Vector{BlockIndex{1}}` instead of `BlockIndexRange{1}`

[mtfishman]

For example:

julia> using BlockArrays

julia> a = mortar([Block(1)[1:2], Block(2)[1:2]])
2-blocked 4-element BlockVector{BlockIndex{1}, Vector{BlockArrays.BlockIndexRange{1, Tuple{UnitRange{Int64}}}}, Tuple{BlockedOneTo{Int64, Vector{Int64}}}}:
 Block(1)[1]
 Block(1)[2]
 ───────────
 Block(2)[1]
 Block(2)[2]

julia> a[Block(1)]
2-element Vector{BlockIndex{1}}:
 Block(1)[1]
 Block(1)[2]

julia> typeof(a[Block(1)])
Vector{BlockIndex{1}} (alias for Array{BlockIndex{1}, 1})

julia> blocks(a)[1]
Block(1)[1:2]

julia> typeof(blocks(a)[1])
BlockArrays.BlockIndexRange{1, Tuple{UnitRange{Int64}}}

julia> import Pkg; Pkg.status("BlockArrays")
Status `.../Project.toml`
  [8e7c35d0] BlockArrays v1.0.1

julia> versioninfo()
Julia Version 1.10.4
Commit 48d4fd48430 (2024-06-04 10:41 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: macOS (arm64-apple-darwin22.4.0)
  CPU: 10 × Apple M1 Max
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-15.0.7 (ORCJIT, apple-m1)
Threads: 1 default, 0 interactive, 1 GC (on 8 virtual cores)

Ideally a[Block(1)] would act like blocks(a)[1] and preserve the type of the block as it was input, i.e. have the type BlockIndexRange{1}.