Display continents filters buttons with countries only

Hide the ones with no linked country

src/routes/__layout.svelte

@@ -50,11 +50,17 @@
                     flag {
                         id
                     }
+                    locations {
+                        slug
+                    }
                 }
 
                 continent {
                     name
                     slug
+                    countries {
+                        slug
+                    }
                 }
 
                 settings {