Clearing workspace while dragging with insertion marker crashes #2338
Description
In playground, create any two connected statement blocks:
On the console, enter:
setTimeout('workspace.clear()', 5000)
In the five seconds before clear runs, grab one of the blocks, disconnect it, and hover it close enough to the other blocks such that an insertion marker appears:
The expected result is that all blocks are deleted.
The actual result is:
Uncaught TypeError: Cannot read property 'setAttribute' of null
at Blockly.InsertionMarkerManager.disconnectMarker_ (insertion_marker_manager.js:666)
at Blockly.InsertionMarkerManager.hidePreview_ (insertion_marker_manager.js:573)
at Blockly.InsertionMarkerManager.maybeHidePreview_ (insertion_marker_manager.js:541)
at Blockly.InsertionMarkerManager.update (insertion_marker_manager.js:243)
at Blockly.BlockDragger.dragBlock (block_dragger.js:211)
at Blockly.BlockDragger.endBlockDrag (block_dragger.js:225)
at Blockly.TouchGesture.Blockly.Gesture.cancel (gesture.js:614)
at Blockly.WorkspaceSvg.cancelCurrentGesture (workspace_svg.js:2347)
at Blockly.BlockSvg.dispose (block_svg.js:874)
at Blockly.WorkspaceSvg.Blockly.Workspace.clear (workspace.js:352)
Line 666. Figures...