Add check before loading metrics data from checkpoint

[blaz-r]

📝 Description

• This PR fixes a problem where AttributeError would occur if model, trained without normalization metrics, was loaded from checkpoint.
• 🛠️ Fixes [Bug]: Checkpoint loading fails when model doesn't use normalization #2253

✨ Changes

Select what type of change your PR is:

• 🐞 Bug fix (non-breaking change which fixes an issue)
• 🔨 Refactor (non-breaking change which refactors the code base)
• 🚀 New feature (non-breaking change which adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to not work as expected)
• 📚 Documentation update
• 🔒 Security update

✅ Checklist

Before you submit your pull request, please make sure you have completed the following steps:

• 📋 I have summarized my changes in the CHANGELOG and followed the guidelines for my type of change (skip for minor changes, documentation updates, and test enhancements).
• 📚 I have made the necessary updates to the documentation (if applicable).
• 🧪 I have written tests that support my changes and prove that my fix is effective or my feature works (if applicable).

For more information about code review checklists, see the Code Review Checklist.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.95%. Comparing base (983ec58) to head (636f399).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2323      +/-   ##
==========================================
+ Coverage   80.93%   80.95%   +0.01%     
==========================================
  Files         247      247              
  Lines       10901    10899       -2     
==========================================
  Hits         8823     8823              
+ Misses       2078     2076       -2     

Flag	Coverage Δ
	80.95% <100.00%> (+0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.