Unfortunately, due to all the server issues we’re having, I really don’t have time to fix that at the moment.
However, whenever I do release an updated version of Weaver Show Posts, which should happen in a month or so to update for WP 5.2, the ‘No Posts found” message will be filtered through a filter called ‘wvr_show_posts_no_posts’. There are plugins that allow you to add filters (PHP code), and you could use this mechanism to change the message to whatever you like – including an empty string.
Show Posts Version 1.5 has the filter as described. It should be available.
You will need to create a child theme or use a plugin that allows you to create PHP filters. The filter passes in the default wording “No Posts Found”. The replacement filter can create any text it wishes.