Avoid null vectors when making colors valid

If the picked color and a forbidden color are identical (like
if they both picked the same palette color and in the special case
when a picked color is outside of the allowed range and the method
returns the picked color as the forbidden color),
the vector between them is zero and the maths for adjusting
the color fails by hitting the iteration limit. This changes
the zero vector to the smallest possible vector in order to
avoid the issue.

This can result in some seriously close adjustments in the case of
picking identical palette colors, which might
be undesirable compared to picking a new palette color.

OpenRA.Mods.Common/ColorValidator.cs

@@ -137,7 +137,14 @@ namespace OpenRA.Mods.Common
 			// Reduce vector by it's biggest value (more calculations, but more accuracy too)
 			var vectorMax = vector.Max(vv => Math.Abs(vv));
 			if (vectorMax == 0)
-				vectorMax = 1;	// Avoid division by 0
+			{
+				vectorMax = 1;  // Avoid division by 0
+
+				// Create a tiny vector to make the while loop maths work
+				vector[0] = 1;
+				vector[1] = 1;
+				vector[2] = 1;
+			}
 
 			vector[0] /= vectorMax;
 			vector[1] /= vectorMax;