Tree-/TableCell: inconsistent edit event firing pattern

in commit/cancelEdit:

     if (table != null)
        // create and fire edit event

in startEdit:
     
     if (column != null)
        // create and fire edit event

digging into history: for cancel, the current pattern (null check of table) was added with JDK-8116392: before it checked column for null

failing test:

     @Test
     public void testEditCancelNoColumn() {
         table.setEditable(true);
         cell.updateTableView(table);
         // force artificially not-empty cell state
         TableCellShim.set_lockItemOnEdit(cell, true);
         CellShim.updateItem(cell, "something", false);
         // start edit: succeeds without firing event (null check
against column)
         cell.startEdit();
         assertTrue(cell.isEditing());
         // cancel edit: NPE from Event.fire - all params
must be != null
         cell.cancelEdit();
         assertFalse(cell.isEditing());
     }

notes:
- the event is fired on the column as target, so the column must not be null
- without guarding against null table, throws NPE due to JDK-8269871 (CellEditEvent is incorrectly? implemented to require !null table)
- same pattern in TreeTableCell which looks like c&p'ed from TableCell

see also: https://mail.openjdk.java.net/pipermail/openjfx-dev/2021-July/031106.html