[16.0] base_search_mail_content: Unable to access collaborator view in tasks within a project as portal user

[Jaimermaccione]

Module

base_search_mail_content

Describe the bug

When a portal user who has been granted collaborator access to a project tries to view the tasks within that project, an error occurs, and no tasks are displayed. The error message is as follows:

Error: Missing field string information for the field 'message_content' from the 'project.task' model
    at http://localhost:16069/web/assets/448-676560f/project.webclient.min.js:6091:258
    at traverse (http://localhost:16069/web/assets/448-676560f/project.webclient.min.js:6086:200)
    at http://localhost:16069/web/assets/448-676560f/project.webclient.min.js:6086:242
    at Function.each (http://localhost:16069/web/assets/439-ba25088/web.assets_common.min.js:173:149)
    at traverse (http://localhost:16069/web/assets/448-676560f/project.webclient.min.js:6086:211)
    at processArch (http://localhost:16069/web/assets/448-676560f/project.webclient.min.js:6090:180)
    at generateLegacyLoadViewsResult (http://localhost:16069/web/assets/448-676560f/project.webclient.min.js:6088:106)
    at http://localhost:16069/web/assets/448-676560f/project.webclient.min.js:3172:447

To Reproduce

Affected versions:
16.0
Steps to reproduce the behavior:

1. Create a project and grant access to a portal user.
2. Log in as that portal user.
3. Access the project to view the tasks within it.
4. Observe the error message.

Expected behavior

The portal user should be able to view the tasks within the project without encountering any errors.

Additional context

Error's screenshot: