ERROR - "arguments.callee" cannot be used in strict mode

[schipa]

Setup

Joomla! 3.7.3
T3 Framework 2.6.6
T3 Bs3 Blank 2.2.6

Problem

I'm getting following output on one of my pages:

Input_0:112: ERROR - "arguments.callee" cannot be used in strict mode
			if(arguments.callee &&
			   ^^^^^^^^^^^^^^^^
Input_0:113: ERROR - "arguments.callee" cannot be used in strict mode
				arguments.callee.caller &&
				^^^^^^^^^^^^^^^^
Input_0:114: ERROR - "arguments.callee" cannot be used in strict mode
				arguments.callee.caller.toString().indexOf('isPropagationStopped') !== -1){	//jquery mark
				^^^^^^^^^^^^^^^^
Input_0:122: ERROR - "arguments.callee" cannot be used in strict mode
			if(arguments.callee &&
			   ^^^^^^^^^^^^^^^^
Input_0:123: ERROR - "arguments.callee" cannot be used in strict mode
				arguments.callee.caller &&
				^^^^^^^^^^^^^^^^
Input_0:124: ERROR - "arguments.callee" cannot be used in strict mode
				arguments.callee.caller.toString().indexOf('isPropagationStopped') !== -1){	//jquery mark
				^^^^^^^^^^^^^^^^
Input_0:132: ERROR - "arguments.callee" cannot be used in strict mode
			if(arguments.callee &&
			   ^^^^^^^^^^^^^^^^
Input_0:133: ERROR - "arguments.callee" cannot be used in strict mode
				arguments.callee.caller &&
				^^^^^^^^^^^^^^^^
Input_0:134: ERROR - "arguments.callee" cannot be used in strict mode
				arguments.callee.caller.toString().indexOf('isPropagationStopped') !== -1){	//jquery mark
				^^^^^^^^^^^^^^^^

It's coming from /plugins/system/t3/base-bs3/js/script.js.

The page with this output is the only one where an iframe is embedded.
Could it be that the scripts interfere? But how?

My workaround for now is to comment out those lines.
I added console.logs but they don't appear in the dev tools.
So I asume it's okay for now!?

[schipa]

When the lines are not commented out, the error message is not in the js console but the whole page (source code) is just the error.

For production I'll keep them commented out for now.
I'll try to setup a testing environment.

[schipa]

http://t3-test.fpgclz.de/ - it's a "T3 Quickstart for Joomla 3.7.3" installation

I found the trigger for said error:

1. edit template style (e.g. "t3_bs3_blank - Home" is used for home page)
2. go to tab "General"
3. under "Optimization" turn "Optimize JS" on
4. as "JS Compress Tool" choose "Closure Compiler"
5. "Save" and watch error

On my production site, I have the same setting turned on. Strange that the error only happend on a single page.

EDIT:
Indeed Google Closure Compiler produces this error message while checking strict mode (https://github.com/google/closure-compiler/blob/master/src/com/google/javascript/jscomp/StrictModeCheck.java#L63)