Fix ImGui::End() placement in EditorManager and ZEML rendering functions

src/app/editor/editor_manager.cc

@@ -263,8 +263,8 @@ absl::Status EditorManager::Update() {
                        editor->active())) {
         current_editor_ = editor;
         status_ = editor->Update();
-        ImGui::End();
       }
+      ImGui::End();
     }
   }
 

src/app/gui/zeml.cc

@@ -388,8 +388,8 @@ void Render(Node& node) {
         for (auto& child : node.children) {
           Render(child);
         }
-        ImGui::End();
       }
+      ImGui::End();
     } break;
     case WidgetType::Button:
       if (node.attributes.data) {