Guard against Seen being undefined when saving config.

exec/imapservice.js

@@ -1441,6 +1441,7 @@ function save_cfg(lck)
 			lock_cfg();
 		cfgfile.rewind();
 		for(sub in saved_config) {
+			if (saved_config[sub].Seen !== undefined) {
 				scpy = JSON.parse(JSON.stringify(saved_config[sub].Seen));
 				s=saved_config[sub].Seen;
 				delete saved_config[sub].Seen;
@@ -1457,6 +1458,7 @@ function save_cfg(lck)
 				}
 				saved_config[sub].Seen=scpy;
 			}
+		}
 		cfgfile.flush();
 		if (lck)
 			unlock_cfg();