Avoid divide by zero

Former-commit-id: cff8caa266353b9074290e878e99e1443e249a45
Former-commit-id: fd97b06cc7eed6df6dd11f1575ea8c810a06f760
Former-commit-id: f3cb76149fcd020a99014762d89820d9a1ea4440

src/ImageProcessor/Colors/Color.cs

@@ -532,6 +532,11 @@ namespace ImageProcessor
         /// <returns>The <see cref="Color"/>.</returns>
         public static Color ToNonPremultiplied(float r, float g, float b, float a)
         {
+            if (Math.Abs(a) < Epsilon)
+            {
+                return new Color(r, g, b, a);
+            }
+
             return new Color(r / a, g / a, b / a, a);
         }