GS.Bands and Divide by zero

[pablosanjose]

Some recent change broke something. This used to work:

h = LP.square() |> hopping(-1)
ϕs = subdiv(0, 0.6π, 2)
b = bands(h, ϕs, ϕs, showprogress = false)
g = h |> attach(@onsite(ω->-im), cells = SA[20,0]) |> greenfunction(GS.Bands(ϕs, ϕs))
gx1 = g(-1)[cellsites(SA[1,-1], 1), cellsites(SA[0,0],1)];

It now gives Divide by zero

EDIT: further reduced the MWE