Blockly toolbox collapse subcategories exception

[samelhusseini]

Exception when adding a new package and a toolbox flyout with a subcategory is open.

Repro steps:

1. Open the Math category and make sure you see the "More" subcategory show up.
2. From the top menu go to Settings -> Add Package. (and not from the Advanced menu).

The following exception occurs:

main.js:10271 Uncaught TypeError: Cannot read property 'getShowLines' of null
    at Blockly.Toolbox.TreeNode.goog.ui.tree.BaseNode.getExpandIconClass (https://pxt.azureedge.net/blob/f18fda6ee99e040d0478bb329470a321c7cb247c/blockly/blockly_compressed.js:959:88)
    at Blockly.Toolbox.TreeNode.goog.ui.tree.BaseNode.updateExpandIcon (https://pxt.azureedge.net/blob/f18fda6ee99e040d0478bb329470a321c7cb247c/blockly/blockly_compressed.js:967:116)
    at Blockly.Toolbox.TreeNode.goog.ui.tree.BaseNode.setExpanded (https://pxt.azureedge.net/blob/f18fda6ee99e040d0478bb329470a321c7cb247c/blockly/blockly_compressed.js:951:199)
    at collapseSubcategories (https://pxt.azureedge.net/blob/7800799a7071ae92302fe70245ee15a1c64ae4b8/pxtblocks.js:3994:25)
    at Blockly.Toolbox.TreeControl.setSelectedItem (https://pxt.azureedge.net/blob/7800799a7071ae92302fe70245ee15a1c64ae4b8/pxtblocks.js:3970:21)
    at Editor.updateToolbox (https://pxt.azureedge.net/blob/4f361dff26d397350d166a0e0319cad2712690d8/main.js:2678:40)
    at https://pxt.azureedge.net/blob/4f361dff26d397350d166a0e0319cad2712690d8/main.js:2140:23
    at <anonymous>
From previous event:
    at Editor.domUpdate (https://pxt.azureedge.net/blob/4f361dff26d397350d166a0e0319cad2712690d8/main.js:2130:18)
    at ProjectView.componentDidUpdate (https://pxt.azureedge.net/blob/4f361dff26d397350d166a0e0319cad2712690d8/main.js:208:21)
    at CallbackQueue.notifyAll (https://pxt.azureedge.net/blob/4f361dff26d397350d166a0e0319cad2712690d8/main.js:44656:22)
    at ReactReconcileTransaction.close (

Exception freezes the editor

[samelhusseini]

This issue only repros in v0. Another way to repro this issue is to have the Blockly flyout open and go to Javascript and back to Blocks.

[samelhusseini]

Fixed in /beta

[lock]

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