User can now go back from the last step of the registration of a sip account when the installation fail.

src/net/java/sip/communicator/plugin/sipaccregwizz/SIPAccountRegistrationWizard.java

@@ -161,7 +161,7 @@ public Iterator getSummary() {
      * @return ProtocolProviderService
      */
     public ProtocolProviderService finish() {
-        firstWizardPage = null;
+        //firstWizardPage = null;
         ProtocolProviderFactory factory
             = SIPAccRegWizzActivator.getSIPProtocolProviderFactory();