Syntax error in jquery-3.2.1.min

Syntax error in jquery-3.2.1.min

I downloaded jquery-3.2.1.min and jquery-3.2.1

After starting a simple HTML-script like this
  1. <!DOCTYPE html>
    <html>
        <head>
            <meta charset="utf-8" />
            <title>R.30's jquery test</title>
            <script src = "../jquery/jquery-3.2.1.min.js"></script>
        </head>
        <body>
            <h1>Here are some tests to be done with <span style = "color: red">jquery</span> ... </h1>
        </body>
    </html>
the firefox console reported hundred times the following error found in the jquery script:
      SyntaxError: test for equality (==) mistyped as assignment (=)?
I changed the script source to jquery-3.2.1.js and restarted the HTML. The console reports this error only one times in line 8068 of the jquery-3.2.1 script.
  1.                     if ( option.selected =
                            jQuery.inArray( jQuery.valHooks.option.get( option ), values ) > -1
                        ) {
                            optionSet = true;
                        }
In fact, there is an assgnment instead of the equality test.I changed '=' to '==' and then the error disappeared after reloading. Is that correct or should it be an identical test ('===')? Please advise.

Other Questions:
Why does this error appears so many times in the compressed file?
Am I the only one who recognized that fault?
How can programmers work with that faulty code? Do they work without debugging? Or do they correct that simple fault without reporting?
Is the code not tested? I mean, such errors should not occur.
Something wrong with my gear? I use WIN10, Firefox 54.0.1 64-bit. But I don't think so.

I'm not sure which Forum is responsible therefore. As I am a newbie, I put it "Gettig started".If it's wrong, please inform the right one.