(core) Clearing selection after rows or cols were removed

Summary:
The selection was not cleared after removing rows, and it still
kept deleted rows ids. Removing selected rows once again
produced an assertion error.
Also, the selection is now cleared when columns are removed.

Test Plan: Updated tests

Reviewers: paulfitz

Reviewed By: paulfitz

Subscribers: paulfitz

Differential Revision: https://phab.getgrist.com/D3623

app/client/components/GridView.js

@@ -299,6 +299,7 @@ GridView.gridCommands = {
     .finally(() => {
       this.cursor.setCursorPos(saved);
       this.cursor.setLive(true);
+      this.clearSelection();
     })
     .catch(reportError);
   },
@@ -719,7 +720,7 @@ GridView.prototype.deleteColumns = function(selection) {
   let actions = fields.filter(col => !col.disableModify()).map(col => ['RemoveColumn', col.colId()]);
   if (actions.length > 0) {
     this.tableModel.sendTableActions(actions, `Removed columns ${actions.map(a => a[1]).join(', ')} ` +
-      `from ${this.tableModel.tableData.tableId}.`);
+      `from ${this.tableModel.tableData.tableId}.`).then(() => this.clearSelection());
   }
 };