MDEV-16990:server crashes in base_list_iterator::next

When we have a query which has implicit_grouping then we are sure that we would end up with only one
row so there is no point to do DISTINCT computation

mysql-test/r/win.result

@@ -3314,3 +3314,15 @@ COUNT(DISTINCT t2.a2)	rank() OVER (ORDER BY t2.b1)
 1	2
 1	3
 DROP TABLE t1,t2;
+#
+# MDEV-16990: server crashes in base_list_iterator::next
+#
+CREATE TABLE t1(i int);
+insert into t1 values (1),(2);
+SELECT DISTINCT row_number() OVER (), MAX(1) FROM t1;
+row_number() OVER ()	MAX(1)
+1	1
+SELECT DISTINCT BIT_AND(0)  OVER (), MAX(1) FROM t1;
+BIT_AND(0)  OVER ()	MAX(1)
+0	1
+drop table t1;

mysql-test/t/win.test

@@ -2082,3 +2082,13 @@ SELECT COUNT(DISTINCT t2.a2),
       rank() OVER (ORDER BY t2.b1)
 FROM t2 ,t1 GROUP BY t2.b1 ORDER BY t1.a1;
 DROP TABLE t1,t2;
+
+--echo #
+--echo # MDEV-16990: server crashes in base_list_iterator::next
+--echo #
+
+CREATE TABLE t1(i int);
+insert into t1 values (1),(2);
+SELECT DISTINCT row_number() OVER (), MAX(1) FROM t1;
+SELECT DISTINCT BIT_AND(0)  OVER (), MAX(1) FROM t1;
+drop table t1;

sql/sql_select.cc

@@ -2731,7 +2731,7 @@ bool JOIN::make_aggr_tables_info()
         remove_duplicates() assumes there is a preceding computation step (and
         in the degenerate join, there's none)
       */
-      if (top_join_tab_count)
+      if (top_join_tab_count && tables_list)
         curr_tab->distinct= true;
 
       having= NULL;