QThread crashes when writing invalid URLs

[EdwinpmDev]

Bug

The app crashes with QThread destroyed while still running when typing text that is not a valid URL in the input.

Steps to reproduce

1. Write any text longer than 10 characters in the input

Cause

The timer triggers the preview thread with any text longer than 10 characters, without validating if it is a real URL.

Pending solution

• Validate that the text begins with http before triggering the preview.
• Cancel previous thread before creating a new one
• Add closeEvent() to clean up threads on closing