Okay, I know what the issue it, just not sure why your install is seeing that. I’ve got a way to fix this possibly.

Could you run a test for me? If you’ve got access to your plugin editor page can you visit it. Or add this to your website url: wp-admin/plugin-editor.php?file=custom-login%2Fincludes%2Fadmin%2Fdashboard.php&plugin=custom-login%2Fcustom-login.php

If you scroll almost to the end of the file and find this section:

elseif ( isset( $_GET['type'] ) && $_GET['type'] === 'js' ) {

	header("content-type:application/x-javascript");
	ob_start();
	str_replace( ob_end_clean(), '', ob_end_clean() );
	$this->jQuery();
	echo ob_get_clean();
	die;
}

and add: if ( !headers_sent() ) on the line before header("content-type:application/x-javascript");

Which should look like:

elseif ( isset( $_GET['type'] ) && $_GET['type'] === 'js' ) {

	if ( !headers_sent() )
		header("content-type:application/x-javascript");
	ob_start();
	str_replace( ob_end_clean(), '', ob_end_clean() );
	$this->jQuery();
	echo ob_get_clean();
	die;
}

If you do so, can you let me know if this solves your issue.