[Bug]: set autocommit=0; prepare execute drop table: a reasonable error message should be displayed.

[tianyahui-python]

Is there an existing issue for the same bug?

• [X] I have checked the existing issues.

Environment

- Version or commit-id (e.g. v0.1.0 or 8b23a93):
- Hardware parameters:
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Actual Behavior

mysql> set autocommit=0; Query OK, 0 rows affected (0.00 sec)

mysql> prepare s7 from 'drop table user'; Query OK, 0 rows affected (0.01 sec)

mysql> execute s7; ERROR 20101 (HY000): internal error: panic runtime error: invalid memory address or nil pointer dereference: runtime.panicmem /usr/local/go/src/runtime/panic.go:260 runtime.sigpanic /usr/local/go/src/runtime/signal_unix.go:835 github.com/matrixorigin/matrixone/pkg/sql/plan.(*VisitPlan).Visit /Users/tianyahui/work_code/go/matrixone/pkg/sql/plan/visit_plan.go:123 github.com/matrixorigin/matrixone/pkg/frontend.(*TxnComputationWrapper).Compile /Users/tianyahui/work_code/go/matrixone/pkg/frontend/mysql_cmd_executor.go:1704 git mysql> deallocate prepare s7; Query OK, 0 rows affected (0.00 sec)

Expected Behavior

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Steps to Reproduce

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Additional information

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