BoundsError: attempt to access 0-element Array{JuMP.Variable,1} at index [1]

i have this function:

function prob(na)
		    b = T0*na
		    total = 0.0
		    for x in Channel(scan)
		        nab = vi2*x + b #the photon numbers for each item in the sum in the note (10)
		        total += prod([c.^complex(n)/factorial(n) for (c, n) in zip(coef, nab)])
		    return abs2.(total*omega)

where na is an integer ,scan is a function with a Channel as an argument → scan(c::Channel) and setc(b)is a function and it is written as follows:

function setc(c)
        for i = 1:size(A, 1)
            m.linconstr[i].lb = float(c[i])   #lb is the lower bound of a variable `x`

A is a non square matrix and lb is a lower bound of a variable x that has this following constraint:

function scan_maker(A)
    m = JuMP.Model(solver=ClpSolver(PrimalTolerance=1e-3, DualTolerance=1e-3, InfeasibleReturn=1, PresolveType=1))
    # m = Model(solver=GurobiSolver())
    level = size(A, 2)
    v = zeros(Int, level)
    ub = zeros(Int, level)
    lb = zeros(Int, level)

    @variable(m, x[1:level])
    @constraint(m, con, A*x.>=0)

now everytime i run the prob function i get this error:
BoundsError: attempt to access 0-element Array{JuMP.Variable,1} at index [1], apparently and according to the stacktrace the error raises in the level of the for loop: for x in Channel(scan) but i don’t know why is there something wrong with the channel i would like to post the scan function too but it is kinda long, could it be the JuMP version that i’m using ? any ideas how to fix the problem?