fix(analysis): Graphite metric provider - index out of range [0] with length 0

[mdsjip]

Rare case, but seen in the wild: Graphite APIs returning response body with just an empty array: []
This PR allows to handle this case by checking it and returning an empty dataPoint array.

Checklist:

• Either (a) I've created an enhancement proposal and discussed it with the community, (b) this is a bug fix, or (c) this is a chore.
• The title of the PR is (a) conventional with a list of types and scopes found here, (b) states what changed, and (c) suffixes the related issues number. E.g. "fix(controller): Updates such and such. Fixes #1234".
• I've signed my commits with DCO
• I have written unit and/or e2e tests for my change. PRs without these are unlikely to be merged.
• My builds are green. Try syncing with master if they are not.
• My organization is added to USERS.md.

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (04b1e30) 81.62% compared to head (8ebd8b4) 81.63%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2751   +/-   ##
=======================================
  Coverage   81.62%   81.63%           
=======================================
  Files         133      133           
  Lines       20157    20160    +3     
=======================================
+ Hits        16454    16457    +3     
  Misses       2849     2849           
  Partials      854      854           

Impacted Files	Coverage Δ
metricproviders/graphite/api.go	78.82% <100.00%> (+0.77%)	⬆️

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[github-actions]

Go Published Test Results

1 950 tests   1 950 ✔️  2m 36s ⏱️
   118 suites         0 💤
       1 files           0 ❌

Results for commit 8ebd8b4.

♻️ This comment has been updated with latest results.

[github-actions]

E2E Tests Published Test Results

    4 files      4 suites   3h 29m 45s ⏱️
  96 tests   82 ✔️   5 💤   9 ❌
402 runs  364 ✔️ 20 💤 18 ❌

For more details on these failures, see this check.

Results for commit 8ebd8b4.

♻️ This comment has been updated with latest results.

[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
0.0% Duplication