[Bug]: query_iterator gives KeyError: 'is_primary' exception

[uncle-yura]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

The problem stated in the issue still exists in version 2.3.4.
As written in this comment, checking the condition causes a KeyError exception.

Here it is necessary to replace
if field[IS_PRIMARY]:
with
if field.get(IS_PRIMARY):
or with
if IS_PRIMARY in field and field[IS_PRIMARY]:

Expected Behavior

No response

Steps/Code To Reproduce behavior

No response

Environment details

- Hardware/Softward conditions (OS, CPU, GPU, Memory):
- Method of installation (Docker, or from source):
- Milvus version (v0.3.1, or v0.4.0):
- Milvus configuration (Settings you made in `server_config.yaml`):

Anything else?

No response