Bug 50022 [DND] NPE in DelegatingDragAdapter
DelegatingDragAdapater defines a list "activeListeners" but initializes it only in DragStart. However, the list is referenced in removeDragSourceListener without a null check, thus causing a null pointer exception if no dragStart ever occured.
bundles/org.eclipse.jface/src/org/eclipse/jface/util/DelegatingDragAdapter.java
}
	/**
	 * Returns the <code>Transfer<code>s from every <code>TransferDragSourceListener</code>.
	 * 
	 * @return the combined <code>Transfer</code>s
	 */
	public Transfer[] getTransfers() {
		Transfer[] types = new Transfer[listeners.size()];
		for (int i = 0; i < listeners.size(); i++) {
			TransferDragSourceListener listener = (TransferDragSourceListener)listeners.get(i);
			types[i] = listener.getTransfer();
		}
		return types;
	}
	/**
	 * Returns <code>true</code> if there are no listeners to delegate drag events to.
	 * 
	 * @return <code>true</code> if there are no <code>TransferDragSourceListeners</code>
	 * 	<code>false</code> otherwise.
	 */
	public boolean isEmpty() {
		return listeners.isEmpty();
	}
	/**
	 * Removes the given <code>TransferDragSourceListener</code>.
	 * Listeners should not be removed while a drag and drop operation is in progress.
	 *  
	 * @param listener the <code>TransferDragSourceListener</code> to remove
	 */
	public void removeDragSourceListener(TransferDragSourceListener listener) {