Stops responding when deleting a line with selected characters

[AMiller42]

If you have multiple lines of code entered, and you select a character, deleting that line will cause everything to stop updating.

To reproduce, enter the following code:

abc
def

Select any character of def, then delete that line.

The browser console returns the following error (Chrome):

Uncaught (in promise) TypeError: Cannot read properties of undefined (reading '2')
    at index-38e4754e.js:21:2484
    at Array.map (<anonymous>)
    at z (index-38e4754e.js:21:2467)
    at Array.flatMap (<anonymous>)
    at Object.p (index-38e4754e.js:19:2540)
    at index-38e4754e.js:4:3975
    at uo (index-38e4754e.js:1:762)
    at Array.forEach (<anonymous>)
    at be (index-38e4754e.js:1:824)
    at Ko (index-38e4754e.js:4:4393)
(anonymous) @ index-38e4754e.js:21
z @ index-38e4754e.js:21
p @ index-38e4754e.js:19
(anonymous) @ index-38e4754e.js:4
uo @ index-38e4754e.js:1
be @ index-38e4754e.js:1
Ko @ index-38e4754e.js:4
p @ index-38e4754e.js:21
qo @ index-38e4754e.js:4
Re @ index-38e4754e.js:4
Promise.then (async)
Go @ index-38e4754e.js:4
Jo @ index-38e4754e.js:4
(anonymous) @ index-38e4754e.js:4
E @ index-38e4754e.js:21
nt @ index-38e4754e.js:19
(anonymous) @ index-38e4754e.js:4
d @ index-38e4754e.js:16