Fix segfault after ALTER UPDATE with Nullable MATERIALIZED column

src/Interpreters/MutationsInterpreter.cpp

@@ -690,9 +690,15 @@ void MutationsInterpreter::prepare(bool dry_run)
                 {
                     if (column.default_desc.kind == ColumnDefaultKind::Materialized)
                     {
+                        auto type_literal = std::make_shared<ASTLiteral>(column.type->getName());
+
+                        auto materialized_column = makeASTFunction("_CAST",
+                            column.default_desc.expression->clone(),
+                            type_literal);
+
                         stages.back().column_to_updated.emplace(
                             column.name,
-                            column.default_desc.expression->clone());
+                            materialized_column);
                     }
                 }
             }

tests/queries/0_stateless/02919_segfault_nullable_materialized_update.reference

@@ -0,0 +1,2 @@
+1	1
+0	0

tests/queries/0_stateless/02919_segfault_nullable_materialized_update.sql

@@ -0,0 +1,15 @@
+DROP TABLE IF EXISTS crash_02919;
+
+CREATE TABLE crash_02919 (
+    b Int64,
+    c Int64 MATERIALIZED b
+)
+ENGINE = MergeTree
+ORDER BY tuple();
+
+INSERT INTO crash_02919 VALUES (1);
+SELECT b, c FROM crash_02919;
+ALTER TABLE crash_02919 UPDATE b = 0 WHERE 1=1 SETTINGS mutations_sync = 1;
+SELECT b, c FROM crash_02919;
+
+DROP TABLE crash_02919;