add memset to prevent race

git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@6053 d0543943-73ff-0310-b7d9-9358b9ac24b2

src/mod/applications/mod_voicemail/mod_voicemail.c

@@ -1651,11 +1651,13 @@ static switch_status_t voicemail_leave_main(switch_core_session_t *session, char
         }
     }
 
+    if (!switch_strlen_zero(buf)) {
         if (!strcasecmp(buf, profile->main_menu_key)) {
             voicemail_check_main(session, profile_name, domain_name, id, 0);
         } else {
             goto greet;
         }
+    }
 
     
     memset(&fh, 0, sizeof(fh));