Fix selection history right-click menu not working (#3819)

https://github.com/rerun-io/rerun/assets/2910679/733bffef-5f52-4152-9e82-1b570af66a0e

- Fixes #1639

crates/re_viewer/src/ui/selection_history_ui.rs

@@ -42,12 +42,18 @@ impl SelectionHistoryUi {
                     item_collection_to_string(blueprint, &previous.selection),
                 ));
 
+            let mut return_current = false;
             let response = response.context_menu(|ui| {
                 // undo: newest on top, oldest on bottom
+                let cur = history.current;
                 for i in (0..history.current).rev() {
                     self.history_item_ui(blueprint, ui, i, history);
                 }
+                return_current = cur != history.current;
             });
+            if return_current {
+                return history.current().map(|sel| sel.selection);
+            }
 
             // TODO(cmc): using the keyboard shortcut should highlight the associated
             // button or something (but then again it, it'd make more sense to do that
@@ -86,12 +92,18 @@ impl SelectionHistoryUi {
                     item_collection_to_string(blueprint, &next.selection),
                 ));
 
+            let mut return_current = false;
             let response = response.context_menu(|ui| {
                 // redo: oldest on top, most recent on bottom
+                let cur = history.current;
                 for i in (history.current + 1)..history.stack.len() {
                     self.history_item_ui(blueprint, ui, i, history);
                 }
+                return_current = cur != history.current;
             });
+            if return_current {
+                return history.current().map(|sel| sel.selection);
+            }
 
             // TODO(cmc): using the keyboard shortcut should highlight the associated
             // button or something (but then again it, it'd make more sense to do that