Safari macOS.- Error in 4.0.3 using dropdownParent argument in definition - TypeError: m.css is not a function

[rosorrentino]

Prerequisites

• [X ] I have searched for similar issues in both open and closed tickets and cannot find a duplicate
• [ X] The issue still exists against the latest master branch of Select2
• [ X] This is not a usage question (Those should be directed to the community)
• [X ] I have attempted to find the simplest possible steos to reproduce the issue
• I have included a failing test as a pull request (Optional)

Steps to reproduce the issue

1. Use Bootstrap and create a modal
2. Add a select2 inside it so add dropdownParent - As described in https://select2.github.io/options.html#dropdownParent
3. Try to use tour dropdown

Expected behavior and actual behavior

No errors

ACTUAL

Error
TypeError: m.css is not a function. (In 'm.css("position")', 'm.css' is undefined)

Environment

Browsers

• Google Chrome
• Mozilla Firefox
• Internet Explorer
• Apple Safari 10.0 from Sierra Developer Preview
  Note same error on Safari 9 - Mac OS X 10.11.5

It does work on Firefox without any error

Operating System

• Windows
• Mac OS X
• Linux
• Mobile

Libraries

• jQuery version: jquery-2.1.4.min
• Select2 version: 4.0.3

Note: This problem is not present using Select2 4.0.0

Isolating the problem

• [ -] This bug happens on the examples page
• There is no modal error
• [ -] The bug happens consistently across all tested browsers
• No only iOS and macOS Safari
• [X ] This bug happens when using Select2 without other pluigns
  Yes

[kevin-brown]

This is almost guaranteed to be a duplicate of #4289 (comment).

[rosorrentino]

PS If anyone sees this one, I had a cache issue with Firefox, it’s for all browsers.