fix: filtered threads indicator not displaying on screen mount

[Rohit3523]

Proposed changes

This PR fixes the issue with the indicator introduced in #6186. Previously, the indicator was rendered only after the filter was applied, but it failed to render when the screen was initially mounted. This PR ensures that the indicator is correctly rendered every time the screen is mounted.

Issue(s)

Closes: #6236

How to test or reproduce

1. Apply a filter in thread in any channel and press back button
2. Go to same channel again and click on thread
3. Observe thread icon

Screenshots

Before: https://github.com/user-attachments/assets/8019784b-8852-4868-9f42-f02d8de87f49
After: https://github.com/user-attachments/assets/23a31788-4246-4b60-8b55-e3ec57566198

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• Improvement (non-breaking change which improves a current function)
• New feature (non-breaking change which adds functionality)
• Documentation update (if none of the other choices apply)

Checklist

• I have read the CONTRIBUTING doc
• I have signed the CLA
• Lint and unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works (if applicable)
• I have added necessary documentation (if applicable)
• Any dependent changes have been merged and published in downstream modules

Further comments

N/A