fix(vllm metrics): error stack trace

[gitdallas]

closes: https://issues.redhat.com/browse/RHOAIENG-11522

this is a situation that would result in the error stack and ui crash without this change:

Description

prevent ui from crashing. let the query be undefined if it doesn't exist, which will result in an empty data and no errors. vince said he did not want an error message at all as it might convey to the user that it might resolve with a refresh or something.

How Has This Been Tested?

tested code on a previous deploy that would crash the ui on metrics page, it no longer crashes. used MR cluster to test. existing tests still pass.

Test Impact

added a new test using mock data that only contains 1 query and made sure that the 4 charts show up (instead of an error stack page). i also updated the test mock for prometheus/serving to return empty results if the request body includes query=undefined\b as it would in the real endpoint. Here's a screenshot from a test with a missing query resulting in no data for one of the serving endpoints (it still shows the data):

Request review criteria:

test a vllm deploy, view the metrics. also view metrics of other types.

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

[openshift-ci]

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[vconzola]

LGTM.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.44%. Comparing base (b5351a7) to head (8df986a).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3200      +/-   ##
==========================================
+ Coverage   85.39%   85.44%   +0.04%     
==========================================
  Files        1277     1277              
  Lines       28082    28088       +6     
  Branches     7487     7495       +8     
==========================================
+ Hits        23980    23999      +19     
+ Misses       4102     4089      -13     

Files with missing lines	Coverage Δ
...end/src/api/prometheus/kservePerformanceMetrics.ts	98.03% <100.00%> (+0.16%)	⬆️
.../metrics/kserve/content/KserveMeanLatencyGraph.tsx	100.00% <100.00%> (ø)

... and 8 files with indirect coverage changes

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