Fixed SD2-836: Editing span highlight colour generates null reference exception

git-svn-id: svn://svn.sharpdevelop.net/sharpdevelop/branches/2.0@1461 1ccf3a8d-04fe-1044-b7c0-cef0b8235c61

src/AddIns/Misc/HighlightingEditor/Project/Src/EditHighlightingColorDialog.cs

@@ -38,6 +38,9 @@ namespace ICSharpCode.SharpDevelop.Gui {
 		{
 			SetupFromXmlStream(this.GetType().Assembly.GetManifestResourceStream("Resources.ColorDialog.xfrm"));
 			
+			if (color == null) {
+				color = new EditorHighlightColor(true);
+			}
 			Color = color;
 			
 			boldBox   = (CheckBox)ControlDictionary["boldBox"];