Fix posts being incorrectly visible on user page. closes #680

- When no discussions are visible, the query that filters posts by discussion visibility was incorrectly making all posts visible.
- Also hide user profiles altogether if discussions are not visible.

src/Core/Repository/PostRepository.php

@@ -96,6 +96,8 @@ class PostRepository
                         event(new ScopePostVisibility($discussion, $query, $actor));
                     });
                 }
+
+                $query->orWhereRaw('FALSE');
             })
             ->get();