IE is broke on 7.x (7.3) 'vendors' is undefined

[LeeDr]

Kibana version: 7.3 (7.x branch snapshot)

Elasticsearch version: 7.3 (7.x branch snapshot)

Server OS version: Windows 2012 Server

Browser version: IE 11

Browser OS version: Windows 2012 Server

Original install method (e.g. download page, yum, from source, etc.): zip files from Default Distribution

Describe the bug: IE 11 won't load. Shows errors in browser console

Steps to reproduce:

1. try Kibana 7.x on IE 11 (I only tried default distribution at this point, not OSS)
2. Kibana "K" just spins

Expected behavior: Kibana should load (and should show "your browser doesn't meet Kibana security requirements" message).

Screenshots (if relevant):

If IE is set to break on exceptions I get this;

Errors in browser console (if relevant): See screenshots above

Provide logs and/or server output (if relevant):

Any additional context:

[elasticmachine]

Pinging @elastic/kibana-operations

[spalger]

@LeeDr can you upload your vendors.bundle.dll.js file? I'd like to know what is at row 556, column 1700218.

[LeeDr]

@spalger I think this arrow function gave you the clue you needed? If you still need the vendors.bundle.dll.js let me know (I'll have to install that build again to get it).

[LeeDr]

I'm pretty sure this was fixed by #38911 but the latest 7.x snapshot build failed so I can't test that yet.