MDEV-20101 Assertion failure on select @@global.'m2'.replicate_ignore_table;

- Removing the wrong assert
- Re-enabling  multi_source.mdev-8874

Author: abarkov

mysql-test/suite/multi_source/disabled.def

@@ -1 +0,0 @@
-mdev-8874 : MDEV-20101 Assertion failure

mysql-test/suite/sys_vars/r/replicate_ignore_table_basic.result

@@ -46,3 +46,13 @@ SELECT @@GLOBAL.replicate_ignore_table;
 
 # Cleanup.
 SET @@GLOBAL.replicate_ignore_table = @save_replicate_ignore_table;
+#
+# MDEV-20101 Assertion failure on select @@global.'m2'.replicate_ignore_table
+#
+SET NAMES latin1;
+SELECT @@global.'m2'.replicate_ignore_table;
+@@global.'m2'.replicate_ignore_table
+NULL
+Warnings:
+Warning	1617	There is no master connection 'm2'
+Warning	1617	There is no master connection 'm2'

mysql-test/suite/sys_vars/t/replicate_ignore_table_basic.test

@@ -49,3 +49,10 @@ SELECT @@GLOBAL.replicate_ignore_table;
 
 --echo # Cleanup.
 SET @@GLOBAL.replicate_ignore_table = @save_replicate_ignore_table;
+
+--echo #
+--echo # MDEV-20101 Assertion failure on select @@global.'m2'.replicate_ignore_table
+--echo #
+
+SET NAMES latin1;
+SELECT @@global.'m2'.replicate_ignore_table;

sql/sql_class.cc

@@ -2400,7 +2400,6 @@ bool THD::check_string_for_wellformedness(const char *str,
                                           size_t length,
                                           CHARSET_INFO *cs) const
 {
-  DBUG_ASSERT(charset_is_system_charset);
   size_t wlen= Well_formed_prefix(cs, str, length).length();
   if (wlen < length)
   {