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}
```
if (to_nullable && WhichDataType(from_type).isStringOrFixedString())
                done = callOnIndexAndDataType<ToDataType>(from_type->getTypeId(), call, ConvertReturnNullOnErrorTag{});
            else
                done = callOnIndexAndDataType<ToDataType>(from_type->getTypeId(), call, ConvertDefaultBehaviorTag{});
        }
        if (!done)
        {
            
            if (std::is_same_v<ToDataType, DataTypeString>)
            {
                return ConvertImplGenericToString::execute(arguments);
            }
            else
                throw Exception("Illegal type " + arguments[0].type->getName() + " of argument of function " + getName(),
                    ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
        }
        return result_column;
    }
};
/** Function toTOrZero (where T is number of date or datetime type):
  *  try to convert from String to type T through parsing,
  *  if cannot parse, return default value instead of throwing exception.
  * Function toTOrNull will return Nullable type with NULL when cannot parse.
  * NOTE Also need to implement tryToUnixTimestamp with timezone.
  */
template <typename ToDataType, typename Name,
    ConvertFromStringExceptionMode exception_mode,
    ConvertFromStringParsingMode parsing_mode = ConvertFromStringParsingMode::Normal>
class FunctionConvertFromString : public IFunction