[Bug]: Editing of submission meta attributes not allowed if not provided during submission

**Description:**

Currently, EvalAI does not allow editing of submission meta attributes if they were not provided during the initial submission. This is a bug, as users should be able to add or edit meta attributes even if they were not provided initially.

**Steps to reproduce:**

Make a submission without providing a specific field (e.g. a text field).
Attempt to edit the submission.
Observe that editing is not allowed due to the missing field.

**Expected behavior:**

Editing should be allowed even if a field was not provided during the initial submission. The user should be able to add or update the field during the editing process.