Small corrections to LBFGSData constructor

[pkofod]

mem is clamped to positive integers. I'm not sure if it's intentional that no errors are thrown here. In the existing code the memory would be set to 1, but all the variables needed to maintain the approximation were set to something not positive, for example

julia>  LinearOperators.LBFGSData(Float64, 1;mem=-1, inverse=true)
ERROR: ArgumentError: invalid GenericMemory size: too large for system address width
Stacktrace:
 [1] GenericMemory
   @ ./boot.jl:516 [inlined]
 [2] Array
   @ ./boot.jl:578 [inlined]
 [3] Array
   @ ./boot.jl:591 [inlined]
 [4] zeros
   @ ./array.jl:589 [inlined]
 [5] zeros(::Type{Float64}, dims::Int64)
   @ Base ./array.jl:585
 [6] LinearOperators.LBFGSData(T::Type, n::Int64; mem::Int64, scaling::Bool, damped::Bool, inverse::Bool, σ₂::Float64, σ₃::Float64)
   @ LinearOperators ~/.julia/packages/LinearOperators/p7GRU/src/lbfgs.jl:36
 [7] top-level scope
   @ REPL[33]:1

Then, a small mostly theoretical thing. The vectors a and b are Vector{Vector{T)) but if inverse == true you get just a Vector{T}. It works at runtime because julia will convert it by accident because it just widens the type and tries to copy all memory, but there is 0 memory to copy. I just figured it was clearer to actually specify the type directly and not rely on the convert behavior.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.83%. Comparing base (32dbc5e) to head (0131eaa).
⚠️ Report is 77 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #414      +/-   ##
==========================================
- Coverage   95.00%   94.83%   -0.17%     
==========================================
  Files          17       21       +4     
  Lines        1100     1180      +80     
==========================================
+ Hits         1045     1119      +74     
- Misses         55       61       +6     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.