fix bug "get user default language null exception"

src/main/java/com/gitblit/authority/GitblitAuthority.java

diff --git a/src/main/java/com/gitblit/authority/GitblitAuthority.java b/src/main/java/com/gitblit/authority/GitblitAuthority.java
index 904042c..15c23a7 100644
--- a/src/main/java/com/gitblit/authority/GitblitAuthority.java
+++ b/src/main/java/com/gitblit/authority/GitblitAuthority.java
@@ -48,6 +48,7 @@
 import java.util.Date;

 import java.util.HashMap;

 import java.util.List;

+import java.util.Locale;

 import java.util.Map;

 import java.util.ResourceBundle;

 

@@ -852,7 +853,10 @@
 		try {

 			if (mail.isReady()) {

 				Mailing mailing = Mailing.newPlain();

-				mailing.subject = MessageFormat.format(ResourceBundle.getBundle("com.gitblit.wicket.GitBlitWebApp",user.getPreferences().getLocale()).getString("gb.emailClientCertificateSubject"), metadata.serverHostname);

+                if( user.getPreferences().getLocale()!=null )

+                    mailing.subject = MessageFormat.format(ResourceBundle.getBundle("com.gitblit.wicket.GitBlitWebApp",user.getPreferences().getLocale()).getString("gb.emailClientCertificateSubject"), metadata.serverHostname);

+                else

+                    mailing.subject = MessageFormat.format(ResourceBundle.getBundle("com.gitblit.wicket.GitBlitWebApp", Locale.ENGLISH).getString("gb.emailClientCertificateSubject") , metadata.serverHostname);

 				mailing.setRecipients(user.emailAddress);

 				File fileMailTmp = null;

 				String body = null;