Restored clip + Don't crash when something is zero or null

src/Skia/Perspex.Skia/DrawingContextImpl.cs

@@ -123,7 +123,7 @@ namespace Perspex.Skia
             brush.Brush->StrokeLineCap = pen.StartLineCap;
             brush.Brush->StrokeMiterLimit = (float)pen.MiterLimit;
 
-            if (pen.DashStyle != null)
+            if (pen.DashStyle?.Dashes != null)
             {
                 var dashes = pen.DashStyle.Dashes;
                 if (dashes.Count > NativeBrush.MaxDashCount)
@@ -168,12 +168,12 @@ namespace Perspex.Skia
         public void PushClip(Rect clip)
         {
             var rc = SkRect.FromRect(clip);
-            //MethodTable.Instance.PushClip(Handle, ref rc);
+            MethodTable.Instance.PushClip(Handle, ref rc);
         }
 
         public void PopClip()
         {
-            //MethodTable.Instance.PopClip(Handle);
+            MethodTable.Instance.PopClip(Handle);
         }
 
         private readonly Stack<double> _opacityStack = new Stack<double>();

src/Skia/Perspex.Skia/FormattedTextImpl.cs

@@ -56,6 +56,8 @@ namespace Perspex.Skia
 
         public Rect HitTestTextPosition(int index)
         {
+            if (index < 0 || index >= _rects.Count)
+                return new Rect();
             return _rects[index];
         }
 
@@ -89,8 +91,13 @@ namespace Perspex.Skia
             }
             for (var c = 0; c < _text.Length; c++)
                 _rects.Add(_shared->Bounds[c].ToRect());
-            var lastLine = _shared->Lines[_shared->LineCount - 1];
-            _size = new Size(maxX, lastLine.Top + lastLine.Height);
+            if (_shared->LineCount == 0)
+                _size = new Size();
+            else
+            {
+                var lastLine = _shared->Lines[_shared->LineCount - 1];
+                _size = new Size(maxX, lastLine.Top + lastLine.Height);
+            }
         }
 
         void Rebuild()