Js Error in scripts.js – this.ajaxForm is undefined

I’m using a standard installation. Nothing special.
I added a window.onerror function to catch any errors and today I got this:

TypeError: this.ajaxForm is not a function. (In \\\’this.ajaxForm\\\’, \\\’this.ajaxForm\\\’ is undefined

http://xxxxxx/content/plugins/contact-form-7/includes/js/scripts.js?ver=4.5.1

‘lineNumber’ => ’14’,

‘userAgent’ => ‘Mozilla/5.0 (iPhone; CPU iPhone OS 9_3_4 like Mac OS X) AppleWebKit/601.1.46 (KHTML, like Gecko) Version/9.0 Mobile/13G35 Safari/601.1’,
‘appName’ => ‘Netscape’,
‘appVersion’ => ‘5.0 (iPhone; CPU iPhone OS 9_3_4 like Mac OS X) AppleWebKit/601.1.46 (KHTML, like Gecko) Version/9.0 Mobile/13G35 Safari/601.1’,
),