pageIndexStart of selection is set to current page immediatley after …

…selection movement is stored to history.

This fixes problem when selection is moved across pages, and then moved on page (in this case pageIndexStart was set according to the first movement of selection)

lib/data/tools/select.dart

@@ -131,7 +131,7 @@ class SelectResult {
   Path path;
 
   /// The page index when the items were selected.
-  final int pageIndexStart;
+  int pageIndexStart;
 
   SelectResult({
     required this.pageIndex,

lib/pages/editor/editor.dart

@@ -604,6 +604,10 @@ class EditorState extends State<Editor> {
   }
 
   void onDrawUpdate(ScaleUpdateDetails details) {
+    if (dragPageIndex==null){
+      // cursor is somewhere between pages, do not respond until its page will be recognized
+      return;
+    }
     final page = coreInfo.pages[dragPageIndex!];
     Offset position = page.renderBox!.globalToLocal(details.focalPoint);
     Offset offset = position - previousPosition;
@@ -765,6 +769,10 @@ class EditorState extends State<Editor> {
   }
 
   void onDrawEnd(ScaleEndDetails details) {
+    if (dragPageIndex==null){
+      // page cannot be determined from cursor position
+      return;
+    }
     final page = coreInfo.pages[dragPageIndex!];
     bool shouldSave = true;
     setState(() {
@@ -820,6 +828,7 @@ class EditorState extends State<Editor> {
               moveOffset.dy,
             ),
           ));
+          select.selectResult.pageIndexStart=select.selectResult.pageIndex; // set starting page index to current page
         } else {
           shouldSave = false;
           select.onDragEnd(page.strokes, page.images);