MDEV-31030 Assertion `!error' failed in ha_partition::update_row on UPDATE

Removing wrong assertion as division by zero was caused by valid
input.

mysql-test/main/partition.result

@@ -2857,3 +2857,26 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 2	DEPENDENT SUBQUERY	t3	ref_or_null	a1,b	a1	10	func,test.t2.a	198	Using where; Full scan on NULL key
 set optimizer_switch=@tmp_os;
 drop table t1,t2,t3;
+#
+# MDEV-31030 Assertion `!error' failed in ha_partition::update_row on UPDATE
+#
+create table t (c int)
+partition by list (1 div c) (
+partition p0 values in (null),
+partition p values in (1));
+insert ignore into t values (0), (1), (0);
+Warnings:
+Warning	1365	Division by 0
+Warning	1365	Division by 0
+update t set c= 2;
+ERROR 22012: Division by 0
+update ignore t set c= 3;
+Warnings:
+Warning	1365	Division by 0
+Warning	1365	Division by 0
+select * from t;
+c
+0
+0
+1
+drop table t;

mysql-test/main/partition.test

@@ -3068,3 +3068,17 @@ set optimizer_switch=@tmp_os;
 
 drop table t1,t2,t3;
 
+--echo #
+--echo # MDEV-31030 Assertion `!error' failed in ha_partition::update_row on UPDATE
+--echo #
+
+create table t (c int)
+partition by list (1 div c) (
+  partition p0 values in (null),
+  partition p values in (1));
+insert ignore into t values (0), (1), (0);
+--error ER_DIVISION_BY_ZERO
+update t set c= 2;
+update ignore t set c= 3;
+select * from t;
+drop table t;

sql/ha_partition.cc

@@ -4593,7 +4593,6 @@ int ha_partition::update_row(const uchar *old_data, const uchar *new_data)
     so this is not supported for this engine.
   */
   error= get_part_for_buf(old_data, m_rec0, m_part_info, &old_part_id);
-  DBUG_ASSERT(!error);
   DBUG_ASSERT(old_part_id == m_last_part);
   DBUG_ASSERT(bitmap_is_set(&(m_part_info->read_partitions), old_part_id));
 #endif