CalorimeterIslandCluster: avoid complaining about missing readouts

[veprbl]

Briefly, what does this PR introduce?

This fixes a small regression from #1554 pointed out by @wdconinc. Some error messages would appear for detectors that are not using matrices and don't specify "readout" field. This allows the current status quo to continue, but removes the messages.

What kind of change does this PR introduce?

• Bug fix (issue #__)
• New feature (issue #__)
• Documentation update
• Other: __

Please check if this PR fulfills the following:

• Tests for the changes have been added
• Documentation has been added / updated
• Changes have been communicated to collaborators

Does this PR introduce breaking changes? What changes might users need to make to their code?

No

Does this PR change default behavior?

No

[github-actions]

Capybara summary for PR 1559

• rec_dis_10x100_minQ2=0_craterlake
• rec_dis_10x100_minQ2=1000_craterlake_tracking_only
• rec_dis_18x275_minQ2=0_craterlake
• rec_dis_18x275_minQ2=1000_craterlake
• rec_dis_5x41_minQ2=0_craterlake
• rec_e_1GeV_20GeV_craterlake
• rec_pi_1GeV_20GeV_craterlake
  ^{_{Last updated 2024-08-07T11:17-04:00 05e4939}}

[wdconinc]

Looks good to me.

Ultimately the reason why we can't guard m_cfg.readout usage behind existing m_cfg.adjacencyMatrix and m_cfg.peakNeighbourhoodMatrix checks is that it would duplicate error handling for empty readout.

[sonarqubecloud]

Quality Gate failed

Failed conditions
C Maintainability Rating on New Code (required ≥ A)

See analysis details on SonarCloud

Catch issues before they fail your Quality Gate with our IDE extension SonarLint