Cannot set property 'length' of null

Problem

The editor is unusable after this error happens.

To reproduce

1. open segment for editing (segment without target content)
2. close the segment
3. leave the task and open the task again
4. open the same segment for editing

Stack:

rangy-core.js:3042 Uncaught TypeError: Cannot set property 'length' of null
 at updateEmptySelection (rangy-core.js:3042)
 at WrappedSelection.selProto.removeAllRanges (rangy-core.js:3261)
 at WrappedSelection.selProto.setSingleRange (rangy-core.js:3648)
 at constructor.setSingleRangeInEditor (UtilSelection.js?_dc=1568388177581:127)
 at constructor.positionCaretAtEnd (UtilSelection.js?_dc=1568388177581:284)
 at constructor.handleAfterSetValueAndMarkup (Editor.js?_dc=1568388176875:617)
 at constructor.fire (ext-all-debug.js:20731)
 at constructor.dispatch (ext-all-debug.js:57952)
 at constructor.callParent (ext-all-debug.js:12493)
 at constructor.dispatch (ext-all-debug.js:58196)

Solution

Reset the internal range selection on task close/open