Fix CURSOR_NEXT/PREV on emptied DB

libraries/liblmdb/mdb.c

@@ -4935,9 +4935,11 @@ fetchm:
 	case MDB_NEXT:
 	case MDB_NEXT_DUP:
 	case MDB_NEXT_NODUP:
-		if (!(mc->mc_flags & C_INITIALIZED))
+		if (!(mc->mc_flags & C_INITIALIZED)) {
 			rc = mdb_cursor_first(mc, key, data);
-		else
+			if (rc)
+				break;
+		} else
 			rc = mdb_cursor_next(mc, key, data, op);
 		break;
 	case MDB_PREV:
@@ -4945,6 +4947,8 @@ fetchm:
 	case MDB_PREV_NODUP:
 		if (!(mc->mc_flags & C_INITIALIZED)) {
 			rc = mdb_cursor_last(mc, key, data);
+			if (rc)
+				break;
 			mc->mc_flags |= C_INITIALIZED;
 			mc->mc_ki[mc->mc_top]++;
 		}