**Use case**

ClickHouse already throws exception if the data for INSERT is empty:

```
Code: 108. DB::Exception: No data to insert
```

Let's introduce a setting, enabled by default, to control this behavior.
The user will be able to disable it to allow empty INSERTs.

This is useful in some batch scripts.
M(UInt64, max_bytes_before_external_sort, 0, "", 0) \
    M(UInt64, max_bytes_before_remerge_sort, 1000000000, "In case of ORDER BY with LIMIT, when memory usage is higher than specified threshold, perform additional steps of merging blocks before final merge to keep just top LIMIT rows.", 0) \
    M(Float, remerge_sort_lowered_memory_bytes_ratio, 2., "If memory usage after remerge does not reduced by this ratio, remerge will be disabled.", 0) \
    \
    M(UInt64, max_result_rows, 0, "Limit on result size in rows. Also checked for intermediate data sent from remote servers.", 0) \
    M(UInt64, max_result_bytes, 0, "Limit on result size in bytes (uncompressed). Also checked for intermediate data sent from remote servers.", 0) \
    M(OverflowMode, result_overflow_mode, OverflowMode::THROW, "What to do when the limit is exceeded.", 0) \
    \
    /* TODO: Check also when merging and finalizing aggregate functions. */ \
    M(Seconds, max_execution_time, 0, "", 0) \
    M(OverflowMode, timeout_overflow_mode, OverflowMode::THROW, "What to do when the limit is exceeded.", 0) \
    \
    M(UInt64, min_execution_speed, 0, "Minimum number of execution rows per second.", 0) \
    M(UInt64, max_execution_speed, 0, "Maximum number of execution rows per second.", 0) \
    M(UInt64, min_execution_speed_bytes, 0, "Minimum number of execution bytes per second.", 0) \
    M(UInt64, max_execution_speed_bytes, 0, "Maximum number of execution bytes per second.", 0) \
    M(Seconds, timeout_before_checking_execution_speed, 10, "Check that the speed is not too low after the specified time has elapsed.", 0) \
    \
    M(UInt64, max_columns_to_read, 0, "", 0) \
    M(UInt64, max_temporary_columns, 0, "", 0) \
    M(UInt64, max_temporary_non_const_columns, 0, "", 0) \
    \
    M(UInt64, max_subquery_depth, 100, "", 0) \
    M(UInt64, max_pipeline_depth, 1000, "", 0) \
    M(UInt64, max_ast_depth, 1000, "Maximum depth of query syntax tree. Checked after parsing.", 0) \
    M(UInt64, max_ast_elements, 50000, "Maximum size of query syntax tree in number of nodes. Checked after parsing.", 0) \
    M(UInt64, max_expanded_ast_elements, 500000, "Maximum size of query syntax tree in number of nodes after expansion of aliases and the asterisk.", 0) \
    \
    M(UInt64, readonly, 0, "0 - everything is allowed. 1 - only read requests. 2 - only read requests, as well as changing settings, except for the 'readonly' setting.", 0) \
    \