Add some comments to previous commit.

src/net/java/sip/communicator/impl/protocol/sip/CallPeerSipImpl.java

@@ -1398,6 +1398,9 @@ private void reflectConferenceFocus(javax.sip.message.Message message)
 
         if (contactHeader != null)
         {
+            // we must set the value of the parameter as null
+            // in order to avoid wrong generation of the tag - ';isfocus='
+            // as it must be ';isfocus'
             if (getCall().isConferenceFocus())
                 contactHeader.setParameter("isfocus", null);
             else