fix regression introduced in [11881]: redraw is needed for unrendered features to be properly cleared. r=erilem (closes #3224)

git-svn-id: http://svn.openlayers.org/trunk/openlayers@11949 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Renderer/Canvas.js

@@ -145,8 +145,12 @@ OpenLayers.Renderer.Canvas = OpenLayers.Class(OpenLayers.Renderer, {
             if (rendered) {
                 // keep track of what we have rendered for redraw
                 this.features[feature.id] = [feature, style];
-                this.pendingRedraw = true;
             }
+            else {
+                // remove from features tracked for redraw
+                delete(this.features[feature.id]);
+            }
+            this.pendingRedraw = true;
         }
         if (this.pendingRedraw && !this.locked) {
             this.redraw();