a segmentation fault (SIGSEGV) due to a null pointer dereference in Item_field::used_tables() at sql/item.cc:3479

MariaDB repeatedly crashes with a segmentation fault (SIGSEGV) due to a null pointer dereference in Item_field::used_tables() at sql/item.cc:3479, where it accesses field->table->const_table without checking if field or field->table is null. This issue is likely triggered during query optimization involving subqueries, views, or triggers, where field resolution fails or remains uninitialized. The crash indicates a denial-of-service (DoS) vulnerability. A null check should be added at this code location to prevent the crash.