Fix text direction auto format detection and undo

[Amir-P]

It fixes two issues:

1. When users enters a character in an empty line with line style auto text direction is not working correctly
2. When auto format applies the same style the undo is an empty delta and applying it causes exception

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (4c3e95f) 86.42% compared to head (58d7083) 86.56%.
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #191      +/-   ##
==========================================
+ Coverage   86.42%   86.56%   +0.14%     
==========================================
  Files          62       62              
  Lines        9672     9812     +140     
==========================================
+ Hits         8359     8494     +135     
- Misses       1313     1318       +5     

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[Amir-P]

Also there is a small behavioral difference with Google Docs. Google Docs doesn't have an undo for auto text direction and just remove the entered character. Should we change it too? @amantoux

[amantoux]

PTAL

[amantoux]

LTGM