session server BUGIX fix x509 key null print
diff --git a/src/session.c b/src/session.c
index 38d7d09..9091143 100644
--- a/src/session.c
+++ b/src/session.c
@@ -111,13 +111,13 @@
 {
     switch (format) {
     case NC_PRIVKEY_FORMAT_RSA:
-        return "RSA";
+        return " RSA ";
     case NC_PRIVKEY_FORMAT_EC:
-        return "EC";
+        return " EC ";
     case NC_PRIVKEY_FORMAT_X509:
-        return NULL;
+        return " ";
     case NC_PRIVKEY_FORMAT_OPENSSH:
-        return "OPENSSH";
+        return " OPENSSH ";
     default:
         return NULL;
     }