Always reproduced:

```
milovidov-desktop :) create table table_map (a Map(String, String), b String) engine = MergeTree() order by a;

CREATE TABLE table_map
(
    `a` Map(String, String),
    `b` String
)
ENGINE = MergeTree
ORDER BY a

Query id: 8f8120c1-c165-452a-815f-2bcae3957e2a

Ok.

0 rows in set. Elapsed: 0.002 sec. 

milovidov-desktop :) SELECT b FROM table_map WHERE a = map('name', NULL, '', NULL)

SELECT b
FROM table_map
WHERE a = {'name', NULL, '', NULL}
```
{
        const char * function_name = name;
        return [function_name] (
            ColumnsWithTypeAndName & arguments, const DataTypePtr & res_type, const ColumnNullable * nullable_col, size_t )
        {
            const auto & first_col = arguments.front().column.get();
            const auto & result_type = typeid_cast<const EnumType &>(*res_type);
            const ColumnStringType * col = typeid_cast<const ColumnStringType *>(first_col);
            if (col && nullable_col && nullable_col->size() != col->size())
                throw Exception("ColumnNullable is not compatible with original", ErrorCodes::LOGICAL_ERROR);
            if (col)
            {
                const auto size = col->size();
                auto res = result_type.createColumn();
                auto & out_data = static_cast<typename EnumType::ColumnType &>(*res).getData();
                out_data.resize(size);
                auto default_enum_value = result_type.getValues().front().second;
                if (nullable_col)
                {
                    for (const auto i : ext::range(0, size))
                    {
                        if (!nullable_col->isNullAt(i))
                            out_data[i] = result_type.getValue(col->getDataAt(i));
                        else
                            out_data[i] = default_enum_value;
                    }