Prevent zero width pens

Author: tocsoft

src/ImageSharp.Drawing/Processing/Pen.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Six Labors.
+// Copyright (c) Six Labors.
 // Licensed under the Apache License, Version 2.0.
 
 using System;
@@ -39,6 +39,8 @@ public Pen(Color color, float width, float[] pattern)
         /// <param name="pattern">The pattern.</param>
         public Pen(IBrush brush, float width, float[] pattern)
         {
+            Guard.MustBeGreaterThan(width, 0, nameof(width));
+
             this.StrokeFill = brush;
             this.StrokeWidth = width;
             this.pattern = pattern;