Bug 92988 [Viewers] potential NPE in AbstractTreeViewer
I0426, found with FindBugs 1. AbstractTreeViewer line 832 invokes "siblings.length", but the "if" statement above implies that siblings could be null here. 2. StringFieldEditor line 187 does an unnecessary null check since Text.getText() never returns null (FindBugs was using this to point to line 190 as a potential NPE).
bundles/org.eclipse.jface/src/org/eclipse/jface/preference/StringFieldEditor.java
*
     * @param parent the parent
     * @return the text control
     */
    public Text getTextControl(Composite parent) {
        if (textField == null) {
            textField = new Text(parent, SWT.SINGLE | SWT.BORDER);
            textField.setFont(parent.getFont());
            switch (validateStrategy) {
            case VALIDATE_ON_KEY_STROKE:
                textField.addKeyListener(new KeyAdapter() {
                    /* (non-Javadoc)
                     * @see org.eclipse.swt.events.KeyAdapter#keyReleased(org.eclipse.swt.events.KeyEvent)
                     */
                    public void keyReleased(KeyEvent e) {
                        valueChanged();
                    }
                });
                break;
            case VALIDATE_ON_FOCUS_LOST:
                textField.addKeyListener(new KeyAdapter() {
                    public void keyPressed(KeyEvent e) {
                        clearErrorMessage();
                    }
                });
                textField.addFocusListener(new FocusAdapter() {
                    public void focusGained(FocusEvent e) {
                        refreshValidState();
                    }
                    public void focusLost(FocusEvent e) {