Bug 41927 [Dialogs] Selecting in PreferenceDialog generates too many invalid entries
20030825 If you select an entry, close the dialog and then reopen it selecting anotehr entry will result in a "this page has invalid values" although you selected nothing.
bundles/org.eclipse.jface/src/org/eclipse/jface/preference/PreferenceDialog.java
public void setErrorMessage(String newErrorMessage) {
		
		if (errorMessage == null
			? newErrorMessage == null
			: errorMessage.equals(newErrorMessage))
			return;
		errorMessage = newErrorMessage;
		if (errorMessage == null) {
			if (showingError) {
				
				showingError = false;
				messageLabel.setBackground(normalMsgAreaBackground);
				messageLabel.setImage(null);
				titleImage.setImage(
					JFaceResources.getImage(PREF_DLG_TITLE_IMG));
			}
			 
			
			if (message == null)
				
				message = ""; 
			messageLabel.setText(message);
			messageLabel.setImage(messageImage);
			messageLabel.setToolTipText(message);
		} else {
			messageLabel.setText(errorMessage);
			messageLabel.setToolTipText(errorMessage);
			if (!showingError) {
				
				showingError = true;