MDEV-216 lp:976104 - Assertion `0' failed in my_message_sql on UPDATE IGNORE,...

MDEV-216 lp:976104 - Assertion `0' failed in my_message_sql on UPDATE IGNORE, or unknown error on release build

Don't send_error at the end of mysql_multi_update() if select failed.
The error, if there was any, was already sent by mysql_select

mysql-test/r/update_ignore_216.result

+CREATE TABLE t1 ( a INT, b CHAR(3) );
+INSERT INTO t1 VALUES ( 1, 'foo' );
+CREATE TABLE t2 ( c CHAR(3), d INT );
+INSERT INTO t2 VALUES ( 'foo', 1 );
+UPDATE IGNORE t1, t2 SET b = 'bar', c = 'bar'
+  WHERE a != ( SELECT 1 UNION SELECT 2 );
+Warnings:
+Warning	1242	Subquery returns more than 1 row
+DROP TABLE t1, t2;

mysql-test/t/update_ignore_216.test

+#
+# MDEV-216 lp:976104 - Assertion `0' failed in my_message_sql on UPDATE IGNORE, or unknown error on release build 
+#
+
+CREATE TABLE t1 ( a INT, b CHAR(3) );
+INSERT INTO t1 VALUES ( 1, 'foo' );
+CREATE TABLE t2 ( c CHAR(3), d INT );
+INSERT INTO t2 VALUES ( 'foo', 1 );
+
+UPDATE IGNORE t1, t2 SET b = 'bar', c = 'bar'
+  WHERE a != ( SELECT 1 UNION SELECT 2 );
+
+DROP TABLE t1, t2;

sql/sql_update.cc

@@ -1293,11 +1293,7 @@ bool mysql_multi_update(THD *thd,
   DBUG_PRINT("info",("res: %d  report_error: %d", res, (int) thd->is_error()));
   res|= thd->is_error();
   if (unlikely(res))
-  {
-    /* If we had a another error reported earlier then this will be ignored */
-    result->send_error(ER_UNKNOWN_ERROR, ER(ER_UNKNOWN_ERROR));
     result->abort();
-  }
   delete result;
   thd->abort_on_warning= 0;
   DBUG_RETURN(FALSE);