small update

docs/en/engines/table-engines/mergetree-family/annindexes.md

@@ -102,7 +102,7 @@ ENGINE = MergeTree
 ORDER BY id;
 ```
 !!! note "Note"
-    Table with array field will work faster, but all arrays **must** have same length.
+    Table with array field will work faster, but all arrays **must** have same length. Use [CONSTRAINT](../../../sql-reference/statements/create/table.md#constraints) to avoid errors. For example `CONSTRAINT constraint_name_1 CHECK length(number) = 256`
 
 Parameter `T` is the number of trees which algorithm will create. The bigger it is, the slower (approximately linear) it works (in both `CREATE` and `SELECT` requests), but the better accuracy you get (adjusted for randomness). 
 

src/Storages/MergeTree/CommonANNIndexes.cpp

@@ -229,7 +229,9 @@ bool ANNCondition::checkQueryStructure(const SelectQueryInfo & query)
         query_information = std::move(order_by_info);
     }
 
-    query_information->limit = limit;
+    if (query_information)
+        query_information->limit = limit;
+
     return query_information.has_value();
 }