fix segmentation fault error

[kushalmalani]

Description

Describe the purpose of this pull request.

Fixes nil pointer segmentation fault error on deployment variable modify with no deployments in workspace

🎟 Issue(s)

Related #1592

🧪 Functional Testing

List the functional testing steps to confirm this feature or fix.

📸 Screenshots

Add screenshots to illustrate the validity of these changes.

📋 Checklist

• Rebased from the main (or release if patching) branch (before testing)
• Ran make test before taking out of draft
• Ran make lint before taking out of draft
• Added/updated applicable tests
• Tested against Astro-API (if necessary).
• Tested against Houston-API and Astronomer (if necessary).
• Communicated to/tagged owners of respective clients potentially impacted by these changes.
• Updated any related documentation

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.55%. Comparing base (a0d6ed4) to head (55c4be3).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1600   +/-   ##
=======================================
  Coverage   86.55%   86.55%           
=======================================
  Files         114      114           
  Lines       15935    15935           
=======================================
  Hits        13792    13792           
  Misses       1288     1288           
  Partials      855      855           

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