Handle nothing case

[tmigot]

Allocation test in ARCTR.decrease for PDataKARC{Float64}: Error During Test at D:\a\ARCTR.jl\ARCTR.jl\test\allocation_test.jl:16
Got exception outside of a @test
MethodError: no method matching &(::Nothing, ::Bool)
Closest candidates are:
&(::Any, ::Any, ::Any, ::Any...) at C:\hostedtoolcache\windows\julia\1.7.3\x64\share\julia\base\operators.jl:655
&(::CEnum.Cenum{T}, ::S) where {T<:Integer, S<:Integer} at C:\Users\runneradmin.julia\packages\CEnum\Bqafi\src\operators.jl:9
&(::Missing, ::Bool) at C:\hostedtoolcache\windows\julia\1.7.3\x64\share\julia\base\missing.jl:167
...
Stacktrace:
[1] decrease(X::PDataKARC{Float64}, α::Float64, TR::TrustRegion{Float64})
@ ARCTR D:\a\ARCTR.jl\ARCTR.jl\src\utils\increase_decrease.jl:34