[8.0.0-beta2-rev1/rev14] Broken newly added row when all of rows are trimmed

[aninde]

Description

In a specific situation when we got:

• fixed rows and columns
• all trimmed rows
• a newly added row by Add row below in context menu from the corner

fixed borders overlap bottom header border and selection is shifted or overlapped in the last rev of 8.0.0beta2
but this bug but this error has changed throughout the various revisions. In the 8.0.0-beta2-rev7 is even fixed however, but it can be replicable on the next ones.

Related to #7060 and #7061

Actual result

1. 8.0.0-beta2-rev1 till rev6https://jsfiddle.net/aninde/8cmukzwh/ the worst with an error in the console and cutted row header.
   

2. https://jsfiddle.net/aninde/mw0pe98y/ 8.0.0-beta2-rev14 fixed border overlay bottom header border

3. Current improper result
   https://jsfiddle.net/aninde/2pwr97gq/ - 8.0.0-beta2-rev17 fixed border overlay bottom header border and doubled and shifted fillHandle

Expected result
8.0.0-beta2-rev7 solved no double border and selection looks good

In the current stable 7.4.2 and 8.0.0-beta.1 selection and borders looks good, only autoFill looks doubled and moved horizontally.

Steps to reproduce

1. Open contextMenu on the corner and Add row below

Demo

https://jsfiddle.net/aninde/Ly6vcoag/ - 8.0.0-beta2-rev1 - error in the console Error: Assertion failed: Expecting an unsigned number. on Firefox
https://jsfiddle.net/aninde/b89hxcaj/ - 7.4.2 no double border, but autoFill looks doubled
https://jsfiddle.net/aninde/8g23cfp5/ - 8.0.0-beta.1 no double border, but autoFill looks doubled
https://jsfiddle.net/aninde/mw0pe98y/ 8.0.0-beta2-rev14 doubled border

https://jsfiddle.net/aninde/aLwvqsgb/ - 8.0.0-beta2-rev7 solved

Your environment

• Handsontable version: Firefox 77, Safari 13.1.1, Chrome 83
• Browser Name and version: 8-beta1+
• Operating System: macOS Catalina 10.15

[aninde]

8.0.0-beta2-rev19 solved this issue. https://jsfiddle.net/aninde/zn28hv5o/1/ After adding row when all of them are trimmed there is no double border and errors in the console.