Fix: Add null checks for DOM manipulation to prevent runtime errors

[alok844937-design]

Fixes

• Fixes [Bug] Add Null Checks for DOM Manipulation to Prevent Runtime Errors #301

Description

This PR fixes a bug where DOM elements were accessed without null checks, which could lead to runtime errors when elements are not present in the DOM.

Technical details

• Added null check for searchForm before attaching event listener
• Added null check for selectedEngine before accessing its properties
• Added null checks for query, commercial, and modify elements
• Ensured safe DOM access to prevent runtime crashes

Tests

• Ran the project locally using Live Server
• Verified that the application works correctly
• Checked browser console to ensure no runtime errors
• Confirmed that the code does not crash when DOM elements are missing

Checklist

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• I added or updated unit tests and/or test scripts for the changes I made (if applicable).
• I added or updated documentation (if applicable).
• I tried running the project locally and verified that there are no
  visible errors.

Developer Certificate of Origin

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Developer Certificate of Origin

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