Bug #38798 Assertion mysql_bin_log.is_open() failed in binlog_trans_log_savepos()

The assert is about binlogging must have been activated, but it was
not actually according to the reported how-to-repeat instuctions.
Analysis revealed that binlog_start_trans_and_stmt() was called
without prior testing if binlogging is ON.

Fixed with avoing entering binlog_start_trans_and_stmt() if binlog is
not activated.

mysql-test/r/skip_log_bin.result

@@ -0,0 +1,6 @@
+DROP TABLE IF EXISTS t1, t2;
+set @@session.binlog_format=row;
+create table t1 (a int);
+insert into t1 values (1);
+create table t2 select * from t1;
+drop table t1, t2;

mysql-test/t/skip_log_bin-master.opt

@@ -0,0 +1 @@
+--loose-skip-log-bin

mysql-test/t/skip_log_bin.test

@@ -0,0 +1,25 @@
+#
+# binlog_off.test purpose is to verify that the --skip-log-bin flag
+# works correctly
+#
+
+--disable_warnings
+DROP TABLE IF EXISTS t1, t2;
+--enable_warnings
+
+#
+# Bug #38798 Assertion mysql_bin_log.is_open() failed in 
+#            binlog_trans_log_savepos()
+# Testing that there is no crash.
+# Before BUG#38798, the code for CREATE...SELECT called an internal function to
+# binlog the statement, even with --skip-log-bin. This caused an assertion
+# to be thrown since the binlog was not open.
+
+set @@session.binlog_format=row;
+
+create table t1 (a int);
+insert into t1 values (1);
+create table t2 select * from t1;
+
+# clean-up
+drop table t1, t2;

sql/sql_insert.cc

@@ -3523,7 +3523,8 @@ select_create::prepare(List<Item> &values, SELECT_LEX_UNIT *u)
     temporary table, we need to start a statement transaction.
   */
   if ((thd->lex->create_info.options & HA_LEX_CREATE_TMP_TABLE) == 0 &&
-      thd->current_stmt_binlog_row_based)
+      thd->current_stmt_binlog_row_based &&
+      mysql_bin_log.is_open())
   {
     thd->binlog_start_trans_and_stmt();
   }
@@ -3619,10 +3620,11 @@ select_create::binlog_show_create_table(TABLE **tables, uint count)
   result= store_create_info(thd, &tmp_table_list, &query, create_info);
   DBUG_ASSERT(result == 0); /* store_create_info() always return 0 */
 
-  thd->binlog_query(THD::STMT_QUERY_TYPE,
-                    query.ptr(), query.length(),
-                    /* is_trans */ TRUE,
-                    /* suppress_use */ FALSE);
+  if (mysql_bin_log.is_open())
+    thd->binlog_query(THD::STMT_QUERY_TYPE,
+                      query.ptr(), query.length(),
+                      /* is_trans */ TRUE,
+                      /* suppress_use */ FALSE);
 }
 
 void select_create::store_values(List<Item> &values)