Fix crash with DISTINCT and window functions

src/Processors/QueryPlan/Optimizations/removeRedundantDistinct.cpp

@@ -172,10 +172,14 @@ namespace
             }
 
             if (typeid_cast<const WindowStep *>(current_step))
+            {
+                /// it can be empty in case of 2 WindowSteps following one another
+                if (!dag_stack.empty())
                 {
                     actions_chain.push_back(std::move(dag_stack));
                     dag_stack.clear();
                 }
+            }
 
             if (const auto * const expr = typeid_cast<const ExpressionStep *>(current_step); expr)
                 dag_stack.push_back(expr->getExpression());

tests/queries/0_stateless/03165_distinct_with_window_func_crash.sql

@@ -0,0 +1,25 @@
+DROP TABLE IF EXISTS atable;
+
+CREATE TABLE atable
+(
+    cdu_date Int16,
+    loanx_id String,
+    rating_sp String
+)
+ENGINE = MergeTree
+ORDER BY tuple();
+
+SELECT DISTINCT
+    loanx_id,
+    rating_sp,
+    cdu_date,
+    row_number() OVER (PARTITION BY cdu_date) AS row_number,
+    last_value(cdu_date) OVER (PARTITION BY loanx_id ORDER BY cdu_date ASC) AS last_cdu_date
+FROM atable
+GROUP BY
+    cdu_date,
+    loanx_id,
+    rating_sp
+SETTINGS query_plan_remove_redundant_distinct = 1;
+
+DROP TABLE atable;