Fix 0 model replicas display text

[emilys314]

Closes https://issues.redhat.com/browse/RHOAIENG-384

Description

The initial data retrieve on the modal would skip 0 and default to 1 because it was a falsey check and not a nullish check.

I also saw on the model row details it would show "Unknown" for 0, so i did the same fix there.

How Has This Been Tested?

1. Edit an already deployed model (kserve and/or modelmesh)
2. Set the replicas to 0 ("Number of model server replicas to deploy" field)
3. Save
4. The model row details should show "Model server replicas 0" instead of "Model server replicas Unknown"
5. Edit the model again
6. The "Number of model server replicas to deploy" field should display 0 instead of 1

Test Impact

Very minor change so no tests updated

Request review criteria:

Self checklist (all need to be checked):

• The developer has manually tested the changes and verified that the changes work
• Testing instructions have been added in the PR body (for PRs involving changes that are not immediately obvious).
• The developer has added tests or explained why testing cannot be added (unit or cypress tests for related changes)

If you have UI changes:

• Included any necessary screenshots or gifs if it was a UI change.
• Included tags to the UX team if it was a UI/UX change.

After the PR is posted & before it merges:

• The developer has tested their solution on a cluster by using the image produced by the PR to main

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.29%. Comparing base (f0b961c) to head (5785087).
Report is 18 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3517      +/-   ##
==========================================
- Coverage   85.30%   85.29%   -0.02%     
==========================================
  Files        1354     1354              
  Lines       31085    31091       +6     
  Branches     8682     8684       +2     
==========================================
+ Hits        26517    26519       +2     
- Misses       4568     4572       +4     

Files with missing lines	Coverage Δ
...rojects/ModelMeshSection/ServingRuntimeDetails.tsx	96.42% <100.00%> (ø)
...d/src/pages/modelServing/screens/projects/utils.ts	93.54% <100.00%> (ø)

... and 4 files with indirect coverage changes

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[christianvogt]

/lgtm
/approve

[openshift-ci]

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