Fix for undetectable encodings (#10884)

[trickster026]

Description

Fixes an issue where the email handler would fail when processing emails with undetectable character encodings. The error occurred when chardet.detect() returned None for the encoding, causing a NoneType error.

Fixes #10884

Type of change

• 🐛 Bug fix (non-breaking change which fixes an issue)

Verification Process

To ensure the changes are working as expected:

• Test Location: [tests/unused/unit/handler_tests/test_email_handler.py]
• Verification Steps:
  1. Run the test suite: pytest tests/unused/unit/handler_tests/test_email_handler.py::TestEmailHandler::test_undetectable_encoding_handling -v
  2. The test verifies that:
     • Emails with undetectable encodings are processed without raising exceptions
     • The result contains all expected fields
     • The handler gracefully handles binary content in email bodies

Checklist:

• My code follows the style guidelines(PEP 8) of MindsDB.
• I have appropriately commented on my code, especially in complex areas.
• Necessary documentation updates are either made or tracked in issues.
• Relevant unit and integration tests are updated or added.

[ZoranPandovski]

Thanks

[trickster026]

I have read the CLA Document and I hereby sign the CLA

[martyna-mindsdb]

@hamishfagg
Can you please approve the deployment of this PR?

[martyna-mindsdb]

@trickster026
Please address the errors from Test on Push -- https://github.com/mindsdb/mindsdb/actions/runs/16069587119/job/45351150502?pr=10905

[martyna-mindsdb]

@ZoranPandovski
Can you please review/approve? Thanks.

[trickster026]

Any update on merging this PR @martyna-mindsdb?

The base branch was changed.

[ZoranPandovski]

Hey @trickster026 , thanks this is ready to be merged but you need to point to develop instead of main branch. Can you please do that?