Go to our demo website, add a new contact in the data module, go to an article page, add a contact paragraph in the "extra" column, select the newly created contact. You will get a freemarker error as follows:

FreeMarker template error!

Expression model.contact.web is undefined on line 104, column 63 in templating-kit/paragraphs/teasers/contact.ftl.
The problematic instruction:
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==> ${model.contact.web?html} [on line 104, column 61 in templating-kit/paragraphs/teasers/contact.ftl]
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I have attached my test contact entry.