Docking: on node split, update memorized DockId for currently closed windows (#3716)

Amended by @ocornut with same fix in DockBuilderRemoveNodeChildNodes().

imgui.cpp

@@ -14190,6 +14190,7 @@ void ImGui::DockNodeTreeSplit(ImGuiContext* ctx, ImGuiDockNode* parent_node, ImG
     child_1->SizeRef[split_axis] = ImFloor(size_avail - child_0->SizeRef[split_axis]);
 
     DockNodeMoveWindows(parent_node->ChildNodes[split_inheritor_child_idx], parent_node);
+    DockSettingsRenameNodeReferences(parent_node->ID, parent_node->ChildNodes[split_inheritor_child_idx]->ID);
     DockNodeTreeUpdatePosSize(parent_node, parent_node->Pos, parent_node->Size);
 
     // Flags transfer (e.g. this is where we transfer the ImGuiDockNodeFlags_CentralNode property)
@@ -14815,7 +14816,10 @@ void ImGui::DockBuilderRemoveNodeChildNodes(ImGuiID root_id)
                 if (root_id != 0)
                     DockContextQueueNotifyRemovedNode(ctx, node);
                 if (root_node)
+                {
                     DockNodeMoveWindows(root_node, node);
+                    DockSettingsRenameNodeReferences(node->ID, root_node->ID);
+                }
                 nodes_to_remove.push_back(node);
             }
         }