Fix #8 Allow colors differences with white/black colors (#9)

Author: kylekatarnls

src/Phim/Color.php

@@ -1697,15 +1697,14 @@ public static function getDifference(ColorInterface $color, ColorInterface $comp
     private static function cieLabToHue($a, $b)
     {
 
-
         $bias = 0;
         if ($a >= 0 && $b === 0)
             return 0;
 
         if ($a < 0 && $b === 0)
             return 180;
 
-        if ($a === 0 && $b > 0)
+        if ($a === 0 && $b >= 0)
             return 90;
 
         if ($a === 0 && $b < 0)