dash >= 1.21.0 doesn't load on IE 11

[michaelbabyn]

Describe your context
Please provide us your environment, so we can easily reproduce the issue.

• replace the result of pip list | grep dash below

dash                            1.21.0
dash-core-components            1.17.1
dash-html-components            1.1.4
dash-renderer                   1.9.1
dash-table                      4.11.3

• if frontend related, tell us your Browser, Version and OS

  • OS: Windows 10
  • Browser IE 11
  • Version latest on browserstack

Describe the bug

If I use dash>=1.21.0, my dash app stays stuck on loading with a couple of errors in the dev console