graph_draw crashes with directed graph

Hi,

I am trying to create a simple NxM graph where each vertex is connected to
all of its immediate neighbors with directed edges. When I use graph_draw to
see the graph it crashes if I define the graph to be directed, but works
fine when the graph is not.
Interestingly enough, the problem seems to disappear for very small size
graphs (e.g. 5x5)

I am using version 2.26 on an Ubuntu 16.04 system. See bellow a snippet of
code that recreates the problem.

Thanks,
Vaggelis

    import gi
    gi.require_version('Gtk', '3.0')
    from graph_tool.all import *
    
    if __name__ == '__main__':
    
        dt_dict = {}
    
        g = Graph(directed=False)
    
        dict_v_name_to_v = {}
        g.vertex_properties["name"] = g.new_vertex_property("string")
        g.vertex_properties["pos"] = g.new_vertex_property("vector<double>")
        g.vertex_properties["coords"] =
g.new_vertex_property("vector<double>")
    
        vp = g.vertex_properties
        ep = g.edge_properties
    
        N_LAT = 20
        N_LON = 20
        # Vertices
        for i in range(0, N_LAT):
            for j in range(0, N_LON):
                v_name = str(i) + '_' + str(j)
                v = g.add_vertex()
                dict_v_name_to_v[v_name] = v
                vp["name"][v] = v_name
                vp['pos'][v] = [float(i), float(j)]
                # vp['coords'][v] = (lat_ar[i], lng_ar[j])
                # vp['elev_in_m'][v] = el_ar[i, j]
    
                # Edges
        for j in range(1, N_LON - 1): # long
            jm1 = j - 1
            jp1 = j + 1
            for i in range(1, N_LAT - 1): # lat
                ip1 = i + 1
                im1 = i - 1
                print(str((i, j)))
    
                v_i_jm1 = dict_v_name_to_v[str(i) + '_' + str(jm1)]
                v_i_j = dict_v_name_to_v[str(i) + '_' + str(j)]
                v_i_jp1 = dict_v_name_to_v[str(i) + '_' + str(jp1)]
                v_ip1_jm1 = dict_v_name_to_v[str(ip1) + '_' + str(jm1)]
                v_ip1_j = dict_v_name_to_v[str(ip1) + '_' + str(j)]
                v_ip1_jp1 = dict_v_name_to_v[str(ip1) + '_' + str(jp1)]
                v_im1_jm1 = dict_v_name_to_v[str(im1) + '_' + str(jm1)]
                v_im1_j = dict_v_name_to_v[str(im1) + '_' + str(j)]
                v_im1_jp1 = dict_v_name_to_v[str(im1) + '_' + str(jp1)]
    
                e_i_jm1 = g.add_edge(v_i_j, v_i_jm1)
                e_i_jp1 = g.add_edge(v_i_j, v_i_jp1)
                e_ip1_jm1 = g.add_edge(v_i_j, v_ip1_jm1)
                e_ip1_j = g.add_edge(v_i_j, v_ip1_j)
                e_ip1_jp1 = g.add_edge(v_i_j, v_ip1_jp1)
                e_im1_jm1 = g.add_edge(v_i_j, v_im1_jm1)
                e_im1_j = g.add_edge(v_i_j, v_im1_j)
                e_im1_jp1 = g.add_edge(v_i_j, v_im1_jp1)
    
        graph_draw(g,
                   pos=g.vertex_properties['pos'],
                   # vertex_text=g.vertex_properties["name"],
                   update_layout=False)

I can't reproduce the crash here... Do you have a GDB stack trace of the
segfault?