Distinct value detection for vertex display should map "0" to white/transparent/undercolour

[gdevenyi]

If I Display an object with something like AAL,

Input /opt/quarantine/resources/CIVET/CIVET_1.12_left.obj
Objects input.
Identified 40/40962 distinct values.
    #     Label  Fr.   R   G   B
    0)     0.00 0.00   0   0 254
    1)     1.00 0.01   0 254   0
    2)     3.00 0.03 254   0   0
    3)     5.00 0.06 254  96 202
    4)     7.00 0.08 246 211  87
    5)     9.00 0.10   0 254 211
    6)    11.00 0.12   0   0  96
    7)    13.00 0.15 254 237 254
    8)    15.00 0.17 105   0   8
    9)    17.00 0.19   0 149 254
   10)    19.00 0.21  26 123   0
   11)    21.00 0.24 254 149 123
   12)    23.00 0.26 237   0 254
   13)    25.00 0.28   0 202 237
   14)    27.00 0.30 211 254   0
   15)    29.00 0.33 105  87   8
   16)    31.00 0.35 123  96 254
   17)    33.00 0.37 246  26  96
   18)    35.00 0.39 131  79 131
   19)    39.00 0.44 149 184 140
   20)    43.00 0.48 140 246 123
   21)    45.00 0.51 254 140   0
   22)    47.00 0.53  35   0  26
   23)    49.00 0.55 228 175 254
   24)    51.00 0.57 140   0 149
   25)    53.00 0.60 158 123 114
   26)    55.00 0.62   0  61   8
   27)    57.00 0.64 167  79   8
   28)    59.00 0.66 167   0  96
   29)    61.00 0.69  96 131 175
   30)    63.00 0.71   0  52 105
   31)    65.00 0.73 149 184  26
   32)    67.00 0.75   0   0 167
   33)    69.00 0.78 228 123 158
   34)    79.00 0.89 254 219 167
   35)    81.00 0.91  52  35   8
   36)    83.00 0.93 175 254 246
   37)    85.00 0.96   0 149 140
   38)    87.00 0.98 228 254 158
   39)    89.00 1.00   0 167 105

The "0" value gets a colour, but really, it should probably get no colour, since its the "no label" state.