Handle empty ranges in RelativeEnvelopeLon() Interval calculation.

Author: awulkiew

Visual_Studio_2015/GraphicalDebugging/ExpressionDrawer.cs

@@ -68,8 +68,18 @@ public Settings CopyColored(System.Windows.Media.Color color)
 
         private static Geometry.Interval RelativeEnvelopeLon(Geometry.IRandomAccessRange<Geometry.Point> points, bool closed, Geometry.Unit unit)
         {
+            Geometry.Interval result = null;
+
+            if (points.Count < 1)
+            {
+                result = new Geometry.Interval();
+                Geometry.AssignInverse(result);
+                return result;
+            }
+
             double x0 = points[0][0];
-            Geometry.Interval result = new Geometry.Interval(x0);
+            result = new Geometry.Interval(x0);
+
             int count = points.Count + (closed ? 1 : 0);
             for (int ii = 1; ii < count; ++ii)
             {

Visual_Studio_2015/GraphicalDebugging/Geometry.cs

@@ -109,6 +109,9 @@ public override string ToString()
 
         public class Interval
         {
+            public Interval()
+            { }
+
             public Interval(double v)
             {
                 Min = v;
@@ -293,6 +296,12 @@ public static void AssignInverse(Box b)
             b.Max = new Point(double.MinValue, double.MinValue);
         }
 
+        public static void AssignInverse(Interval i)
+        {
+            i.Min = double.MaxValue;
+            i.Max = double.MinValue;
+        }
+
         public static Box Aabb(Point p1, Point p2, Unit unit)
         {
             if (unit == Unit.None)