Segfault in `maximum_weight_perfect_matching` when the graph does not have a perfect matching

[etiennedeg]

That's really not a nice behavior :\

~~the fault seems to be on BlossomV.jl side https://github.com/mlewe/BlossomV.jl/issues/25~~

Ok, in fact, the problem seems to originate from Blossom V itself, this is so bad :(

// Computes a perfect matching of minimum cost. // NOTE: a perfect matching of finite cost must exist (otherwise the behaviour is not specified).

We can get around this by adding dummy edges with big weights.