Fix overflow, race condition, and format bugs

pixstrip-gtk/src/steps/step_watermark.rs

@@ -210,6 +210,10 @@ pub fn build_watermark_page(state: &AppState) -> adw::NavigationPage {
             .height_request(48)
             .build();
 
+        btn.update_property(&[
+            gtk::accessible::Property::Label(&format!("Watermark position: {}", name)),
+        ]);
+
         let icon = if i == cfg.watermark_position as usize {
             "radio-checked-symbolic"
         } else {