Track changed state in nav mode combo box (#1703)

* Track changed state in nav mode combo box

* Simplify the code a bit

---------

Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>

crates/re_viewer/src/ui/view_spatial/ui.rs

@@ -276,24 +276,26 @@ impl ViewSpatialState {
                 .on_hover_text("The virtual camera which controls what is shown on screen.");
             ui.vertical(|ui| {
                 let mut nav_mode = *self.nav_mode.get();
-                let nav_mode_response =  egui::ComboBox::from_id_source("nav_mode")
+                let mut changed = false;
+                egui::ComboBox::from_id_source("nav_mode")
                     .selected_text(nav_mode)
                     .show_ui(ui, |ui| {
                         ui.style_mut().wrap = Some(false);
                         ui.set_min_width(64.0);
 
-                        ui.selectable_value(
+                        changed |= ui.selectable_value(
                             &mut nav_mode,
                             SpatialNavigationMode::TwoD,
                             SpatialNavigationMode::TwoD,
-                        );
-                        ui.selectable_value(
+                        ).changed();
+
+                        changed |= ui.selectable_value(
                             &mut nav_mode,
                             SpatialNavigationMode::ThreeD,
                             SpatialNavigationMode::ThreeD,
-                        );
-                    }).response;
-                    if nav_mode_response.changed() {
+                        ).changed();
+                    });
+                    if changed {
                         self.nav_mode = EditableAutoValue::UserEdited(nav_mode);
                     }