[Regression in 1.1.1] Uncaught TypeError: Cannot read property '0' of undefined(…) when using backspace to remove a character

[eamodio]

Since I've updated to 1.1.1 I get this error: (1.1.0 was fine)

quill.js:2890 Uncaught TypeError: Cannot read property '0' of undefined(…)
fix_cursor @ quill.js:2890
diff_main @ quill.js:2531
Delta.diff @ quill.js:2397
(anonymous function) @ quill.js:3549update @ quill.js:3558
(anonymous function) @ quill.js:1702modify @ quill.js:2083
(anonymous function) @ quill.js:1701
emit @ quill.js:4913emit @ quill.js:4801
update @ quill.js:6043
(anonymous function) @ quill.js:1141

Steps for Reproduction

1. Enter some text
2. Hit backspace to delete the text
3. Observe the error :)

Expected behavior:
No error

Actual behavior:
Error

Platforms:
macOS Sierra, Chrome Version 54.0.2840.71 (64-bit)

Version:
1.1.1

[benbro]

Caused by this PR:
jhchen/fast-diff#2