Parse Exponent stop-opacity

Stop crash on null or empty images
Deal with multiple spaces in Matrix

Source/External/ExCSS/Lexer.cs

@@ -710,13 +710,17 @@ namespace ExCSS
         }
 
         private Block NumberFraction(char current)
-        {
+        {
             while (true)
             {
                 if (current.IsDigit())
                 {
                     _buffer.Append(current);
                 }
+                else if ("eE%-".IndexOf(current) >= 0)
+                {
+                    break;
+                }
                 else if (current.IsNameStart())
                 {
                     var number = FlushBuffer();

Source/Filter Effects/SvgFilter.cs

@@ -124,6 +124,10 @@ namespace Svg.FilterEffects
             var inflate = 0.5f;
             var transform = GetTransform(element);
             var bounds = GetPathBounds(element, renderer, transform);
+
+            if (bounds.Width == 0 || bounds.Height == 0)
+                return;
+
             var buffer = new ImageBuffer(bounds, inflate, renderer, renderMethod) { Transform = transform };
 
             IEnumerable<SvgFilterPrimitive> primitives = this.Children.OfType<SvgFilterPrimitive>();
@@ -137,7 +141,7 @@ namespace Svg.FilterEffects
 
                 // Render the final filtered image
                 var bufferImg = buffer.Buffer;
-                bufferImg.Save(@"C:\test.png");
+                //bufferImg.Save(@"C:\test.png");
                 var imgDraw = RectangleF.Inflate(bounds, inflate * bounds.Width, inflate * bounds.Height);
                 var prevClip = renderer.GetClip();
                 renderer.SetClip(new Region(imgDraw));

Source/Filter Effects/feColourMatrix/SvgColourMatrix.cs

@@ -33,7 +33,10 @@ namespace Svg.FilterEffects
 
         public override void Process(ImageBuffer buffer)
 		{
-            var inputImage = buffer[this.Input];
+            var inputImage = buffer[this.Input];
+
+            if (inputImage == null)
+                return;
 
             float[][] colorMatrixElements;
             float value;
@@ -75,7 +78,7 @@ namespace Svg.FilterEffects
                     };
                     break;
                 default: // Matrix
-                    var parts = this.Values.Split(new char[] { ' ', '\t', '\n', '\r', ',' });
+                    var parts = this.Values.Replace("  ", " ").Split(new char[] { ' ', '\t', '\n', '\r', ',' });
                     colorMatrixElements = new float[5][];
                     for (int i = 0; i < 4; i++)
                     {