MDEV-17021 Server crash or assertion `length <= column->length' failure in write_block_record

Problem was that the number of NULL bit's was record wrong in the
.frm file because there could be more fields marked NOT_NULL after the
number of not_null fields where recorded.

Fixed by copying test for virtual fields from prepare_create_field()
The code change, only the test, doesn't have to be merged to 10.3
as this is fixed there.

mysql-test/suite/maria/create.result

+CREATE OR REPLACE TABLE t1 ( 
+f1 DECIMAL(43,0) NOT NULL,
+f2 TIME(4) NULL,
+f3 BINARY(101) NULL,
+f4 TIMESTAMP(4) NULL,
+f5 DATETIME(1) NULL,
+f6 SET('a','b','c') NOT NULL DEFAULT 'a',
+f7 VARBINARY(2332) NOT NULL DEFAULT '',
+f8 DATE NULL,
+f9 BLOB NULL,
+f10 MEDIUMINT(45) NOT NULL DEFAULT 0,
+f11 YEAR NULL,
+f12 BIT(58) NULL,
+v2 TIME(1) AS (f2) VIRTUAL,
+v3 BINARY(115) AS (f3) VIRTUAL,
+v4 TIMESTAMP(3) AS (f4) VIRTUAL,
+v7 VARBINARY(658) AS (f7) PERSISTENT,
+v8 DATE AS (f8) PERSISTENT,
+v9 TINYTEXT AS (f9) PERSISTENT,
+v11 YEAR AS (f11) VIRTUAL
+) ENGINE=Aria;
+INSERT IGNORE INTO t1 (f1,f2,f3,f4,f5,f6,f7,f8,f9,f10,f11,f12) VALUES
+(0.8,'16:01:46',NULL,'2006-03-01 12:44:34','2029-10-10 21:27:53','a','foo','1989-12-24','bar',9,1975,b'1');
+Warnings:
+Note	1265	Data truncated for column 'f1' at row 1
+DROP TABLE t1;

mysql-test/suite/maria/create.test

+--source include/have_maria.inc
+
+# MDEV-17021
+# Server crash or assertion `length <= column->length' failure in
+# write_block_record
+#
+
+CREATE OR REPLACE TABLE t1 (
+  f1 DECIMAL(43,0) NOT NULL,
+  f2 TIME(4) NULL,
+  f3 BINARY(101) NULL,
+  f4 TIMESTAMP(4) NULL,
+  f5 DATETIME(1) NULL,
+  f6 SET('a','b','c') NOT NULL DEFAULT 'a',
+  f7 VARBINARY(2332) NOT NULL DEFAULT '',
+  f8 DATE NULL,
+  f9 BLOB NULL,
+  f10 MEDIUMINT(45) NOT NULL DEFAULT 0,
+  f11 YEAR NULL,
+  f12 BIT(58) NULL,
+  v2 TIME(1) AS (f2) VIRTUAL,
+  v3 BINARY(115) AS (f3) VIRTUAL,
+  v4 TIMESTAMP(3) AS (f4) VIRTUAL,
+  v7 VARBINARY(658) AS (f7) PERSISTENT,
+  v8 DATE AS (f8) PERSISTENT,
+  v9 TINYTEXT AS (f9) PERSISTENT,
+  v11 YEAR AS (f11) VIRTUAL
+) ENGINE=Aria;
+INSERT IGNORE INTO t1 (f1,f2,f3,f4,f5,f6,f7,f8,f9,f10,f11,f12) VALUES
+ (0.8,'16:01:46',NULL,'2006-03-01 12:44:34','2029-10-10 21:27:53','a','foo','1989-12-24','bar',9,1975,b'1');
+DROP TABLE t1;

sql/sql_table.cc

@@ -3328,6 +3328,10 @@ mysql_prepare_create_table(THD *thd, HA_CREATE_INFO *create_info,
       }
     }
 
+    /* Virtual fields are always NULL */
+    if (sql_field->vcol_info)
+      sql_field->flags&= ~NOT_NULL_FLAG;
+
     if (sql_field->sql_type == MYSQL_TYPE_SET ||
         sql_field->sql_type == MYSQL_TYPE_ENUM)
     {