Merge pull request #121 from mayorovad/overlays-stories-fix

Fix stories with overlays usage

packages/html/stories/Overlays.stories.js

@@ -62,7 +62,7 @@ const Template = ({ label, ...args }) => {
     if (cell != null) {
       const overlays = graph.getCellOverlays(cell);
 
-      if (overlays == null) {
+      if (overlays.length == 0) {
         // Creates a new overlay with an image and a tooltip
         const overlay = new CellOverlay(
           new ImageBox('/images/check.png', 16, 16),

packages/html/stories/Thread.stories.js

@@ -61,7 +61,7 @@ const Template = ({ label, ...args }) => {
   const f = () => {
     const overlays = graph.getCellOverlays(v1);
 
-    if (overlays == null) {
+    if (overlays.length == 0) {
       graph.removeCellOverlays(v2);
       graph.setCellWarning(v1, 'Tooltip');
     } else {