Index: dataobj/umgebung.cc
===================================================================
--- dataobj/umgebung.cc	(リビジョン 6356)
+++ dataobj/umgebung.cc	(作業コピー)
@@ -348,7 +348,7 @@
 		plainstring str = nickname.c_str();
 		file->rdwr_str(str);
 		if (file->is_loading()) {
-			nickname = str.c_str();
+			nickname = str ? str.c_str() : "";
 		}
 	}
 	// server settings are not saved, since the are server specific and could be different on different servers on the save computers