window: Limit HeaderBar to min width as nat width

Before we were doing the same with just the title in the HeaderBar. This
gave problems with correctly measuring for ADW_CENTERING_POLICY_LOOSE.

src/widgets/image/rotation.rs

@@ -26,7 +26,7 @@ impl imp::LpImage {
         }
 
         self.rotation.set(rotation);
-        obj.configure_adjustments();
+        self.configure_adjustments();
         obj.notify_rotation();
         obj.queue_draw();
     }