Use = null rather that delete to clear out excanvas context (problem

reported by ryleyb)


git-svn-id: https://flot.googlecode.com/svn/trunk@291 1e0a6537-2640-0410-bfb7-f154510ff394

jquery.flot.js

@@ -704,7 +704,7 @@
              // the state on them manually
             if (window.G_vmlCanvasManager)
                 placeholder.find("canvas").each(function () {
-                    delete this.context_;
+                    this.context_ = null;
                 });
             
             placeholder.html(""); // clear placeholder