MDEV-24796 Assertion `page_has_next... failed in btr_pcur_store_position()

In commit eaeb8ec4 (MDEV-24653)
an incorrect debug assertion was introduced.

btr_pcur_store_position(): If the only record in the page is the
instant ALTER TABLE metadata record, we cannot expect there to be
a successor page. The situation could be improved by MDEV-24673 later.

mysql-test/suite/innodb/r/instant_alter_debug.result

@@ -303,5 +303,19 @@ SELECT * FROM t1;
 a	b	c
 DROP TABLE t1;
 SET GLOBAL innodb_limit_optimistic_insert_debug = @saved_limit;
+#
+# MDEV-24796 Assertion page_has_next... failed
+# in btr_pcur_store_position()
+#
+CREATE TABLE t1 (c INT KEY) ENGINE=InnoDB;
+INSERT INTO t1 VALUES(1),(2);
+SET GLOBAL innodb_limit_optimistic_insert_debug=2;
+ALTER TABLE t1 ADD COLUMN d INT;
+DELETE FROM t1;
+InnoDB		0 transactions not purged
+SELECT * FROM t1 WHERE c<>1 ORDER BY c DESC;
+c	d
+DROP TABLE t1;
+SET GLOBAL innodb_limit_optimistic_insert_debug = @saved_limit;
 # End of 10.3 tests
 SET GLOBAL innodb_purge_rseg_truncate_frequency = @save_frequency;

mysql-test/suite/innodb/t/instant_alter_debug.test

@@ -348,6 +348,22 @@ SELECT * FROM t1;
 DROP TABLE t1;
 SET GLOBAL innodb_limit_optimistic_insert_debug = @saved_limit;
 
+--echo #
+--echo # MDEV-24796 Assertion page_has_next... failed
+--echo # in btr_pcur_store_position()
+--echo #
+
+CREATE TABLE t1 (c INT KEY) ENGINE=InnoDB;
+INSERT INTO t1 VALUES(1),(2);
+SET GLOBAL innodb_limit_optimistic_insert_debug=2;
+ALTER TABLE t1 ADD COLUMN d INT;
+DELETE FROM t1;
+--source include/wait_all_purged.inc
+SELECT * FROM t1 WHERE c<>1 ORDER BY c DESC;
+DROP TABLE t1;
+
+SET GLOBAL innodb_limit_optimistic_insert_debug = @saved_limit;
+
 --echo # End of 10.3 tests
 
 SET GLOBAL innodb_purge_rseg_truncate_frequency = @save_frequency;

storage/innobase/btr/btr0pcur.cc

@@ -169,9 +169,6 @@ btr_pcur_store_position(
 			ut_ad(!page_has_prev(block->frame));
 			rec = page_rec_get_next(rec);
 			if (page_rec_is_supremum(rec)) {
-				ut_ad(page_has_next(block->frame)
-				      || block->page.id.page_no()
-				      != index->page);
 				goto before_first;
 			}
 		}