MDEV-6769 DROP TRIGGER IF NOT EXIST binlogged on master but not on slave

don't return from DROP TRIGGER IF NOT EXISTS on the slave side
early when the trigger couldn't be read

Author: vuvova

mysql-test/suite/rpl/r/rpl_trigger.result

@@ -986,4 +986,15 @@ Warning	1196	Some non-transactional changed tables couldn't be rolled back
 include/diff_tables.inc [master:t1, slave:t1]
 include/diff_tables.inc [master:log, slave:log]
 drop table t1, log;
+drop trigger if exists notexistent;
+Warnings:
+Note	1360	Trigger does not exist
+include/show_binlog_events.inc
+Log_name	Pos	Event_type	Server_id	End_log_pos	Info
+master-bin.000001	#	Gtid	#	#	GTID #-#-#
+master-bin.000001	#	Query	#	#	use `test`; drop trigger if exists notexistent
+include/show_binlog_events.inc
+Log_name	Pos	Event_type	Server_id	End_log_pos	Info
+slave-bin.000001	#	Gtid	#	#	GTID #-#-#
+slave-bin.000001	#	Query	#	#	use `test`; drop trigger if exists notexistent
 include/rpl_end.inc

mysql-test/suite/rpl/t/rpl_trigger.test

@@ -532,6 +532,19 @@ connection master;
 drop table t1, log;
 sync_slave_with_master;
 
+#
+# MDEV-6769 DROP TRIGGER IF NOT EXIST binlogged on master but not on slave
+#
+let $slave_pos= query_get_value(SHOW MASTER STATUS, Position, 1);
+connection master;
+let $binlog_start= query_get_value(SHOW MASTER STATUS, Position, 1);
+drop trigger if exists notexistent;
+source include/show_binlog_events.inc;
+sync_slave_with_master;
+let $binlog_start= $slave_pos;
+source include/show_binlog_events.inc;
+connection master;
+
 #
 # End of tests
 #

sql/sql_parse.cc

@@ -2283,11 +2283,15 @@ mysql_execute_command(THD *thd)
           according to slave filtering rules.
           Returning success without producing any errors in this case.
         */
-        DBUG_RETURN(0);
+        if (!thd->lex->check_exists)
+          DBUG_RETURN(0);
+        /*
+          DROP TRIGGER IF NOT EXISTS will return without an error later
+          after possibly writing the query to a binlog
+        */
       }
-      
-      // force searching in slave.cc:tables_ok() 
-      all_tables->updating= 1;
+      else // force searching in slave.cc:tables_ok()
+        all_tables->updating= 1;
     }
 
     /*