Do not wrap_visibleVisualLines over _allVisualLines

Taking a look to the original avalonedit's textview, when creating the readonlycollection for the _visibleVisualLines it doesn't wrap a collection over the _allVisualLines.

It uses .ToArray() to make the _visibleVisualLines to be a new collection.

src/AvaloniaEdit/Rendering/TextView.cs

@@ -719,7 +719,7 @@ private void ClearVisualLines()
                 }
                 _allVisualLines.Clear();
 
-                _visibleVisualLines = new ReadOnlyCollection<VisualLine>(_allVisualLines);
+                _visibleVisualLines = new ReadOnlyCollection<VisualLine>(_allVisualLines.ToArray());
             }
         }
 
@@ -932,7 +932,7 @@ protected override Size MeasureOverride(Size availableSize)
             {
                 // no document -> create empty list of lines
                 _allVisualLines = new List<VisualLine>();
-                _visibleVisualLines = new ReadOnlyCollection<VisualLine>(_allVisualLines);
+                _visibleVisualLines = new ReadOnlyCollection<VisualLine>(_allVisualLines.ToArray());
                 maxWidth = 0;
             }
             else
@@ -1036,7 +1036,7 @@ private double CreateAndMeasureVisualLines(Size availableSize)
 
             _allVisualLines = _newVisualLines;
             // visibleVisualLines = readonly copy of visual lines
-            _visibleVisualLines = new ReadOnlyCollection<VisualLine>(_newVisualLines);
+            _visibleVisualLines = new ReadOnlyCollection<VisualLine>(_newVisualLines.ToArray());
             _newVisualLines = null;
 
             if (_allVisualLines.Any(line => line.IsDisposed))