Bug 273012 [Forms] NPE in FormPage.setActive(...)
bundles/org.eclipse.ui.forms/src/org/eclipse/ui/forms/editor/FormPage.java
/**
	 * Implemented by testing if the managed form is dirty.
	 * 
	 * @return <code>true</code> if the managed form is dirty,
	 *         <code>false</code> otherwise.
	 * 
	 * @see org.eclipse.ui.ISaveablePart#isDirty()
	 */
	public boolean isDirty() {
		return mform != null ? mform.isDirty() : false;
	}
	/**
	 * Preserves the page index.
	 * 
	 * @param index
	 *            the assigned page index
	 */
	public void setIndex(int index) {
		this.index = index;
	}
	/**
	 * Returns the saved page index.
	 * 
	 * @return the page index
	 */
	public int getIndex() {
		return index;
	}
	/**
	 * Form pages are not editors.