Another issue with the Birkhoff example

[pokutta]

Where does this warning come from? See below. Run is for n = 5, k = 2.

julia> include("examples/birkhoff.jl")
seed = 0x6a330cff07fe872a
WARNING: redefinition of constant Xstar. This may fail, cause incorrect answers, or produce other errors.

Boscia Algorithm.

Parameter settings.
	 Tree traversal strategy: Move best bound
	 Branching strategy: Most infeasible
	 Absolute dual gap tolerance: 1.000000e-06
	 Relative dual gap tolerance: 1.000000e-02
	 Frank-Wolfe subproblem tolerance: 1.000000e-05
	 Total number of varibales: 102
	 Number of integer variables: 0
	 Number of binary variables: 50


---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
   Iteration       Open          Bound      Incumbent      Gap (abs)      Gap (rel)       Time (s)      Nodes/sec        FW (ms)       LMO (ms)  LMO (calls c)   FW (Its)   #ActiveSet  Discarded
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
*          1          2  -3.894415e-05   1.349569e+00   1.349608e+00            Inf   2.137900e+01   1.403246e-01          21219          17564             55       4784           19         13
*          4          5  -3.894415e-05   1.349569e+00   1.349608e+00            Inf   5.068500e+01   1.775673e-01           7981           1412            131      10001           13         26
*          5          6  -3.894415e-05   1.004665e+00   1.004704e+00            Inf   6.806100e+01   1.616197e-01          17373          12415            181       7460           20         22
*         14         15  -2.863835e-06   7.464572e-01   7.464600e-01            Inf   1.568910e+02   1.848417e-01          13856           9112            476       7169           19         26
*         21         22  -2.863835e-06   6.242914e-01   6.242942e-01            Inf   2.198940e+02   1.955488e-01          12339           7930            691       6572           20         16
WARNING: Dual bound 4.01031 is larger than the objective of the primal solution 4. The solution might not be optimal.
*         25         26  -2.863835e-06   6.048654e-01   6.048683e-01            Inf   2.549260e+02   2.000581e-01           8620           6118            828       3718           25          9
*         28         29  -2.863835e-06   5.440530e-01   5.440559e-01            Inf   2.826500e+02   2.016628e-01           7998           1277            915      10001           12         28