### Apache Airflow version

2.1.3 (latest released)

### Operating System

Debian Buster

### Versions of Apache Airflow Providers

_No response_

### Deployment

Managed Services (Astronomer, Composer, MWAA etc.)

### Deployment details

Running `quay.io/astronomer/ap-airflow:2.1.3-buster` Docker image

### What happened

In the task attributes view of a BashOperator, the `template_ext` row doesn't show any value, while I would expect to see `('.sh', '.bash')`.

![image](https://user-images.githubusercontent.com/6249654/131467817-8620f68d-0f3d-491d-ad38-cbf5b91cdcb3.png)


### What you expected to happen

Expect to see correct `template_ext` value

### How to reproduce

Run a BashOperator and browse to Instance Details --> scroll down to `template_ext` row

### Anything else

Spent a little time trying to figure out what could be the reason, but haven't found the problem yet. Therefore created issue to track.

### Are you willing to submit PR?

- [X] Yes I am willing to submit a PR!

### Code of Conduct

- [X] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)

airflow/models/baseoperator.py
"""Returns reference to XCom pushed by current operator"""
        from airflow.models.xcom_arg import XComArg
        return XComArg(operator=self)
    @staticmethod
    def xcom_push(
        context: Any,
        key: str,
        value: Any,
        execution_date: Optional[datetime] = None,
    ) -> None:
        """
        Make an XCom available for tasks to pull.
        :param context: Execution Context Dictionary
        :type: Any
        :param key: A key for the XCom
        :type key: str
        :param value: A value for the XCom. The value is pickled and stored
            in the database.
        :type value: any pickleable object
        :param execution_date: if provided, the XCom will not be visible until
            this date. This can be used, for example, to send a message to a
            task on a future date without it being immediately visible.
        :type execution_date: datetime
        """
        context['ti'].xcom_push(key=key, value=value, execution_date=execution_date)
    @staticmethod
    def xcom_pull(