Dropdown breaks editable datatable layout on Firefox

[NIX-Pepe]

I'm submitting a ... (check one with "x")

[ x] bug report => Search github for a similar issue or PR before submitting
[ ] feature request => Please check if request is not on the roadmap already https://github.com/primefaces/primeng/wiki/Roadmap
[ ] support request => Please do not submit support request here, instead see http://forum.primefaces.org/viewforum.php?f=35

Current behavior
If primeng editable table demo is opened in FF 45 (https://www.primefaces.org/primeng/#/datatable/editable) you can see that there are added multiple empty columns right of sale date column. There will be more empty columns added to right side of sale date, if there are more rows.
Note, that this behavior only occurs, if there is more than one additional column right to brand column containing a drop down menu. It does not occur if there is no drop down or only one column after a column comprising a drop down menu. Additionally it only seems to happen in FF. If I open demo site in chromium there are no empty columns. All columns specified are expanded to full width of table.

Expected behavior
Same as in chromium, no empty columns added by adding additional rows. All columns expanded to full width of table.

Minimal reproduction of the problem with instructions
Step 1: Open demo in FF 45: https://www.primefaces.org/primeng/#/datatable/editable
Step 2: Open demo in Chromium/Chrome: https://www.primefaces.org/primeng/#/datatable/editable

What is the motivation / use case for changing the behavior?
It is weird for an enduser to see tables shrinking by adding new rows to them.

Please tell us about your environment:
FF 45, Debian Strech, angular-cli/ng serve...

• Angular version:
  Angular 4

• PrimeNG version:
  primeng@4.0.0

• Browser:
  Chrome 58.0.3029.81
  Firefox 45.9.0

• Language: TypeScript:
  tsc --version
  Version 2.2.1

• Node (for AoT issues): node --version =
  node --version
  v7.0.0