[Py-client] Fix dataset contains null value contract error

[HTHou]

Description

To reproduce:

1. execute the following sql

create database root.ln

CREATE ALIGNED TIMESERIES root.ln.g1.d1(BOOLEAN BOOLEAN encoding=PLAIN compressor=SNAPPY, INT32 INT32 encoding=PLAIN compressor=SNAPPY, INT64 INT64 encoding=PLAIN compressor=SNAPPY, FLOAT FLOAT encoding=PLAIN compressor=SNAPPY, DOUBLE DOUBLE encoding=PLAIN compressor=SNAPPY, TEXT TEXT encoding=PLAIN compressor=SNAPPY, TS TIMESTAMP encoding=PLAIN compressor=SNAPPY, DATE DATE encoding=PLAIN compressor=SNAPPY, BLOB BLOB encoding=PLAIN compressor=SNAPPY, STRING STRING encoding=PLAIN compressor=SNAPPY)

insert into root.ln.g1.d1(timestamp, BOOLEAN, INT32, INT64, FLOAT, DOUBLE, TEXT, TS, DATE, BLOB, STRING) aligned values(1, true, 1, 1, 1.0, 1.0, '1', 1, '1971-01-01', X'', '1')
insert into root.ln.g1.d1(timestamp, STRING) aligned values(2, 'None')

2. execute the following python script

from iotdb.Session import Session

session = Session("127.0.0.1", "6667", "root", "root", 1024, "UTC+8", False)
 
session.open(False)
 
with session.execute_query_statement(
        "select * from root.**"
    ) as session_data_set:
        session_data_set.set_fetch_size(1024)
        while session_data_set.has_next():
            print(session_data_set.next())
 
session.close()

You will see an error.

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 40.93%. Comparing base (d359e0d) to head (6fec871).
Report is 6 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #13762      +/-   ##
============================================
- Coverage     40.94%   40.93%   -0.01%     
  Complexity       71       71              
============================================
  Files          4038     4038              
  Lines        252818   252818              
  Branches      30855    30855              
============================================
- Hits         103518   103493      -25     
- Misses       149300   149325      +25     

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