Fix mistake 2

src/Core/Settings.h

@@ -439,7 +439,7 @@ class IColumn;
     M(String, output_format_avro_codec, "", "Compression codec used for output. Possible values: 'null', 'deflate', 'snappy'.", 0) \
     M(UInt64, output_format_avro_sync_interval, 16 * 1024, "Sync interval in bytes.", 0) \
     M(Bool, output_format_tsv_crlf_end_of_line, false, "If it is set true, end of line in TSV format will be \\r\\n instead of \\n.", 0) \
-    M(Bool, output_format_tsv_null_representation, "\\N", "Custom null representation in TSV format", 0) \
+    M(String, output_format_tsv_null_representation, "\\N", "Custom null representation in TSV format", 0) \
     \
     M(UInt64, input_format_allow_errors_num, 0, "Maximum absolute amount of errors while reading text formats (like CSV, TSV). In case of error, if at least absolute or relative amount of errors is lower than corresponding value, will skip until next line and continue.", 0) \
     M(Float, input_format_allow_errors_ratio, 0, "Maximum relative amount of errors while reading text formats (like CSV, TSV). In case of error, if at least absolute or relative amount of errors is lower than corresponding value, will skip until next line and continue.", 0) \