SIGSEGV in dict_index_t::reconstruct_fields()

#0  0x000055635ccef651 in dict_index_t::reconstruct_fields()::{lambda(dict_field_t const&)#1}::operator()(dict_field_t const&) const (o=

      @0x61a00000a9e0: {col = 0xbebebebebebebebe, name = {m_name = 0xbebebebebebebebe <error: Cannot access memory at address 0xbebebebebebebebe>}, prefix_len = 3774, fixed_len = 1003, descending = 0}, __closure=0x7fffda7bcbf0)

    at /mariadb/10.8/storage/innobase/dict/dict0mem.cc:1209

1209					{ return o.col->ind == c.ind(); });

diff --git a/mysql-test/suite/innodb/t/instant_alter_crash.test b/mysql-test/suite/innodb/t/instant_alter_crash.test

index 43db8f619f3..75f26a80559 100644

--- a/mysql-test/suite/innodb/t/instant_alter_crash.test

+++ b/mysql-test/suite/innodb/t/instant_alter_crash.test

@@ -184,6 +184,12 @@ CREATE TABLE t3(id INT PRIMARY KEY, c2 INT, v2 INT AS(c2) VIRTUAL, UNIQUE(v2))

 ENGINE=InnoDB;

 INSERT INTO t3 SET id=1,c2=1;

+CREATE TABLE t4(id INT PRIMARY KEY,c2 INT,c3 INT,c4 INT,c5 INT,c6 INT,c7 INT)

+ENGINE=InnoDB;

+INSERT INTO t4 SET id=1;

+ALTER TABLE t4 DROP c4, MODIFY c5 INT AFTER c2, ADD (c8 INT, c9 INT),

+ALGORITHM=INSTANT;

+

 SET DEBUG_SYNC='innodb_alter_inplace_before_commit SIGNAL ddl WAIT_FOR ever';

 --send

 ALTER TABLE t3 ADD COLUMN c3 TEXT NOT NULL DEFAULT 'sic transit gloria mundi';

@@ -198,10 +204,12 @@ INSERT INTO t1 VALUES(0,0);

 disconnect ddl;

 --source include/start_mysqld.inc

+SELECT * FROM t4;

 SHOW CREATE TABLE t1;

 SHOW CREATE TABLE t2;

 SHOW CREATE TABLE t3;

-DROP TABLE t1,t2,t3;

+SHOW CREATE TABLE t4;

+DROP TABLE t1,t2,t3,t4;

 --remove_files_wildcard $MYSQLD_DATADIR/test #sql*.frm

 --list_files $MYSQLD_DATADIR/test

diff --git a/storage/innobase/dict/dict0mem.cc b/storage/innobase/dict/dict0mem.cc

index 8d53f646131..37cf7dc687f 100644

--- a/storage/innobase/dict/dict0mem.cc

+++ b/storage/innobase/dict/dict0mem.cc

@@ -1177,6 +1177,8 @@ inline bool dict_index_t::reconstruct_fields()

 {

 	DBUG_ASSERT(is_primary());

+	const auto old_n_fields{n_fields};

+

 	n_fields = (n_fields + table->instant->n_dropped)

 		& dict_index_t::MAX_N_FIELDS;

 	n_def = (n_def + table->instant->n_dropped)

@@ -1204,11 +1206,11 @@ inline bool dict_index_t::reconstruct_fields()

 		} else {

 			DBUG_ASSERT(!c.is_not_null());

 			const auto old = std::find_if(

-				fields + n_first, fields + n_fields,

+				fields + n_first, fields + old_n_fields,

 				[c](const dict_field_t& o)

 				{ return o.col->ind == c.ind(); });

-			if (old >= fields + n_fields

+			if (old >= fields + old_n_fields

 			    || old->prefix_len

 			    || old->col != &table->cols[c.ind()]) {

 				return true;