Cannot uninstall

Hi there,
We installed SEO by 10Web a couple of months ago.
We need to uninstall it. Unfortunately when I disable and delete or just disable the plugin I get an error when I try to edit a page in WordPress.

I enabled debug on my WordPress and I’m seeing the following error:

[30-Jan-2019 16:46:13 UTC] PHP Catchable fatal error: Object of class __PHP_Incomplete_Class could not be converted to string in /xxxx/ public_html/wp-content/plugins/types/vendor/toolset/toolset-common/toolset-forms/classes/class.types.php on line 540

Can you help?

Thanks,
Alan