So are you actually trying to connect to the URL in the Details section of your image ?
If not what URL are you trying to connect to (just the domain name) no http or www so the link isn't active ?
That said the URL looks like it is a 3rd party Ad and they are a source (outside of many sites control) that could well be malicious (malvertising, malicious ads), so you wouldn't want to disable the domain. Though it is possible to add that domain and or the domain you are visiting, this shouldn't be done lightly as the potential risk has to be weighed against excluding a site (which is essentially the only way to disable the alert/s for that site).
See
https://www.google.co.uk/search?q=showcasead.com for more general information on that domain.
You could also use the Reporting Possible False Positive File or Website -
https://www.avast.com/false-positive-file-form.php form. That would generate a review but there is no guarantee it would be considered a false positive.