Added StrokeWidth check to SvgVisualElement.RenderStroke.

RenderStroke method won't render the stroke if StrokeWidth is less or equal zero.

Source/Basic Shapes/SvgVisualElement.cs

@@ -215,7 +215,7 @@ namespace Svg
         /// <param name="renderer">The <see cref="ISvgRenderer"/> object to render to.</param>
         protected internal virtual bool RenderStroke(ISvgRenderer renderer)
         {
-            if (this.Stroke != null && this.Stroke != SvgColourServer.None)
+            if (this.Stroke != null && this.Stroke != SvgColourServer.None && this.StrokeWidth > 0)
             {
                 float strokeWidth = this.StrokeWidth.ToDeviceValue(renderer, UnitRenderingType.Other, this);
                 using (var brush = this.Stroke.GetBrush(this, renderer, Math.Min(Math.Max(this.StrokeOpacity * this.Opacity, 0), 1), true))