(core) Fixing cursor position for filtered linked section.

Summary:
In a selector table, when a selected row is filtered out of view, linked widgets should update based on the newly selected row.
There were a few bugs that contributed to this wrong behavior:
- Gridview wasn't subscribing to the current row id, and the row with id 'new' was being converted to the first row
- Cursor was keeping track of the currently selected row id, it was hiding a problem behind the proper rowIndex
- Undo/redo somehow leveraged the wrong rowId from the cursor during the position restore.

The `No data` text was also changed to be more meaningful.

Test Plan: Added and updated.

Reviewers: georgegevoian

Reviewed By: georgegevoian

Differential Revision: https://phab.getgrist.com/D3937

app/client/components/GristDoc.ts

@@ -476,6 +476,7 @@ export class GristDoc extends DisposableWithEvents {
       const viewId = toKo(ko, this.activeViewId)();
       if (!isViewDocPage(viewId)) { return null; }
       const section = this.viewModel.activeSection();
+      if (section?.isDisposed()) { return null; }
       const view = section.viewInstance();
       return view;
     })));
@@ -620,6 +621,11 @@ export class GristDoc extends DisposableWithEvents {
   public async setCursorPos(cursorPos: CursorPos) {
     if (cursorPos.sectionId && cursorPos.sectionId !== this.externalSectionId.get()) {
       const desiredSection: ViewSectionRec = this.docModel.viewSections.getRowModel(cursorPos.sectionId);
+      // If the section id is 0, the section doesn't exist (can happen during undo/redo), and should
+      // be fixed there. For now ignore it, to not create empty sections or views (peeking a view will create it).
+      if (!desiredSection.id.peek()) {
+        return;
+      }
       // If this is completely unknown section (without a parent), it is probably an import preview.
       if (!desiredSection.parentId.peek() && !desiredSection.isRaw.peek()) {
         const view = desiredSection.viewInstance.peek();