LDAP: Make sure we do not send empty description field, replace " \n" with null

git-svn-id: http://svn.code.sf.net/p/davmail/code/trunk@713 3d1905a2-6b24-0410-a738-b14d5a86fcbd

src/java/davmail/exchange/ExchangeSession.java

@@ -2733,6 +2733,8 @@ public class ExchangeSession {
                     } catch (ParseException e) {
                         throw new IOException(e);
                     }
+                } else if ("textdescription".equals(propertyName) && " \n".equals(propertyValue)) {
+                    propertyValue = null;
                 }
                 if (propertyValue != null && propertyValue.length() > 0) {
                     item.put(propertyName, propertyValue);