MDEV-30681 SIGFPE / UBSAN runtime error: division by zero in String::needs_conversion on ALTER

The problem was earlier fixed by MDEV-30805. Adding an MTR test only.

mysql-test/main/partition_charset.result

@@ -39,5 +39,17 @@ t1	CREATE TABLE `t1` (
 (PARTITION `p0` VALUES LESS THAN ('a') ENGINE = MyISAM)
 DROP TABLE t1;
 #
+# MDEV-30681 SIGFPE / UBSAN runtime error: division by zero in String::needs_conversion on ALTER
+#
+CREATE TABLE t1 (a BINARY (10)) PARTITION BY LIST COLUMNS (a) (PARTITION p VALUES IN (0xFF));
+SELECT COLUMN_TYPE, COLLATION_NAME FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME='t1';
+COLUMN_TYPE	COLLATION_NAME
+binary(10)	NULL
+ALTER TABLE t1 CHANGE COLUMN a a CHAR(10) BINARY;
+SELECT COLUMN_TYPE, COLLATION_NAME FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME='t1';
+COLUMN_TYPE	COLLATION_NAME
+char(10)	latin1_bin
+DROP TABLE t1;
+#
 # End of 10.9 tests
 #

mysql-test/main/partition_charset.test

@@ -43,6 +43,17 @@ ALTER TABLE t1 CHANGE COLUMN a a CHAR BINARY;
 SHOW CREATE TABLE t1;
 DROP TABLE t1;
 
+--echo #
+--echo # MDEV-30681 SIGFPE / UBSAN runtime error: division by zero in String::needs_conversion on ALTER
+--echo #
+
+CREATE TABLE t1 (a BINARY (10)) PARTITION BY LIST COLUMNS (a) (PARTITION p VALUES IN (0xFF));
+SELECT COLUMN_TYPE, COLLATION_NAME FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME='t1';
+ALTER TABLE t1 CHANGE COLUMN a a CHAR(10) BINARY;
+SELECT COLUMN_TYPE, COLLATION_NAME FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME='t1';
+DROP TABLE t1;
+
+
 --echo #
 --echo # End of 10.9 tests
 --echo #