Divizion by Zero Exception

[Akinmayowa Akinyemi]

If any of the data items are zero, a division by zero exception occurs.

    data = [0, 0, 0, 0, 0]
    v_labels = ["line1", "line2", "line3", "line4", "line5", "line6", "line7"]
    h_labels = ["Yes", "No", "Maybe", "Someday", "Hmm"]

    CairoPlot.bar_plot ('vbar.png', data,
                        280, 190,
                        border = 10, grid = True, rounded_corners = True) #,

Attached is a patch to fix the issue