fix: fixed crash issue for post in learner tab

[sundasnoreen12]

INF-1316

Description

An unexpected error occurs appear when attempting to create a new post from the learners' tab.

Steps to reproduce.

Create a post from the learners tab and you will see this error

Solution

Crash issue has been fixed.

Merge Checklist

• [ ] If your update includes visual changes, have they been reviewed by a designer? Send them a link to the Sandbox, if applicable.
• [ ] Is there adequate test coverage for your changes?

Post-merge Checklist

• [ ] Deploy the changes to prod after verifying on stage or ask @openedx/edx-infinity to do it.
• [ ] 🎉 🙌 Celebrate! Thanks for your contribution.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 92.82%. Comparing base (80073e3) to head (3beba66).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #684 +/- ## ======================================= Coverage 92.82% 92.82% ======================================= Files 158 158 Lines 3304 3304 Branches 896 896 ======================================= Hits 3067 3067 Misses 218 218 Partials 19 19 ```

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