Bug 61713 MessageDialog can't be created in non UI thread anymore
I20040511 In the past it was possible to create a MessageDialog from non UI threads. This is not possible with I20040511 anymore. Doing so now results in an invalid thread access to due the fact that the images are now managed by SWT.
bundles/org.eclipse.jface/src/org/eclipse/jface/resource/ImageRegistry.java
entry = new Entry();
			putEntry(key, entry);
		}
		if (entry.image == null && entry.descriptor == null) {
			entry.image = image;
			return;
		}
		throw new IllegalArgumentException("ImageRegistry key already in use: " + key); 
	}
	/**
	 * Removes an image from this registry.  
     * If an SWT image was allocated, it is disposed.
	 * This method has no effect if there is no image or descriptor for the given key.
	 * @param key the key
	 */
	public void remove(String key) {
		if (table == null)
			return;
		Entry entry = (Entry) getTable().remove(key);
		if (entry != null) {
		    if (entry.image != null && !entry.image.isDisposed()) {
		        entry.image.dispose();
		    }
		    entry.image = null;
		}
	}
	/**
	 * Contains the data for an entry in the registry. 
	 */
	private static class Entry {