Now handles values of none without throwing an exception. This bug could cause...

Now handles values of none without throwing an exception. This bug could cause images to load very slowly.

Source/DataTypes/SvgUnit.cs

@@ -23,6 +23,11 @@ namespace Svg
         /// </summary>
         public static readonly SvgUnit Empty = new SvgUnit();
 
+        /// <summary>
+        /// Gets an <see cref="SvgUnit"/> with a value of none.
+        /// </summary>
+        public static readonly SvgUnit None = new SvgUnit(SvgUnitType.None,0f);
+
         /// <summary>
         /// Gets a value to determine whether the unit is empty.
         /// </summary>
@@ -179,6 +184,8 @@ namespace Svg
 
             switch (this.Type)
             {
+                case SvgUnitType.None:
+                    return "none";
                 case SvgUnitType.Pixel:
                     type = "px";
                     break;
@@ -256,6 +263,10 @@ namespace Svg
     /// </summary>
     public enum SvgUnitType
     {
+        /// <summary>
+        /// Indicates that the unit holds no value.
+        /// </summary>
+        None,
         /// <summary>
         /// Indicates that the unit is in pixels.
         /// </summary>

Source/DataTypes/SvgUnitCollection.cs

@@ -39,7 +39,9 @@ namespace Svg
 
                 foreach (string point in points)
                 {
-                    units.Add((SvgUnit)_unitConverter.ConvertFrom(point.Trim()));
+                    SvgUnit newUnit = (SvgUnit)_unitConverter.ConvertFrom(point.Trim());
+                    if(newUnit != SvgUnit.None)
+                        units.Add(newUnit);
                 }
 
                 return units;

Source/DataTypes/SvgUnitConverter.cs

@@ -29,6 +29,9 @@ namespace Svg
             string unit = (string)value;
             int identifierIndex = -1;
 
+            if (unit == "none")
+                return SvgUnit.None;
+
             for (int i = 0; i < unit.Length; i++)
             {
                 if (char.IsLetter(unit[i]) || unit[i] == '%')