Bug 130854 [CellEditors] JFace TableViewer ignoring ICellEditor validator state
Using a validator on a TextCellEditor and entering invalid text into a cell results in ICellModifier.modify() being called with a null value, rather than an error being reported and the value being discarded. TableEditorImpl.saveEditorValue() *does actually check for editor validity*, but in the case of invalid values does nothing but no-op with comment "///Do what ???" and then calls cellEditor.getValue() which, for TextCellEditor's anyway, always returns null if its validator has invalidated the current value.
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/ColumnViewerEditor.java
if (timeout != 0) {
					activationTime = activationEvent.time + timeout;
				} else {
					activationTime = 0;
				}
				if (editorActivationListener != null
						&& !editorActivationListener.isEmpty()) {
					Object[] ls = editorActivationListener.getListeners();
					for (int i = 0; i < ls.length; i++) {
						((ColumnViewerEditorActivationListener) ls[i])
								.beforeEditorActivated(activationEvent);
						
						if (activationEvent.cancel) {
							return false;
						}
					}
				}
				updateFocusCell(cell, activationEvent);
				cellEditor.addListener(cellEditorListener);
				part.getEditingSupport().initializeCellEditorValue(cellEditor,
						cell);
				
				
				
				
				
				final Control control = cellEditor.getControl();
				cellEditor.activate(activationEvent);
				if (control == null) {
					return false;