pam: make sure we pass a valid tty field to logind

diff --git a/src/pam-module.c b/src/pam-module.c
index 1658348e28ec922e5568204d07be9c838bbc46fd..ad8ca91d03fe412c2b596b86d58c6ff8239f3c01 100644 (file)
--- a/src/pam-module.c
+++ b/src/pam-module.c
@@ -389,7 +389,7 @@ _public_ PAM_EXTERN int pam_sm_open_session(
 
                 if (isempty(display))
                         display = tty;
-                tty = NULL;
+                tty = "";
         }
 
         type = !isempty(display) ? "x11" :