Steps to reproduce:

1. Create a dashboard and add "Graph (classic)";
2. Confirm changes in graph widget;
3. Try to select some area in classic graph widget using sBox.

Result:
In Google Chrome and Opera (with small changes):

Uncaught TypeError: Cannot set property 'prevent_refresh' of null
at HTMLImageElement.selectionHandlerDragStart (jsLoader.php:881)
at HTMLDocument.dispatch (jsLoader.php:4979)
at HTMLDocument.v.handle (jsLoader.php:4979)

In Firefox:

TypeError: data is null

Expected:
sBox zoom should be disabled in Dashboard edit mode.