Fix 500 error loading environments index

Previously loading the environments index page would show a 500 error
when two conditions were met:

1. The associated cluster deployment had no pods
2. Reactive caching has cached the state of the deployment data.

Previously the filtering of pods by project environment were only run if
there were pods present, but this special case isn't needed as the
filter already handles empty arrays.

Closes https://gitlab.com/gitlab-org/gitlab/-/issues/216118

changelogs/unreleased/sh-handle-deployments-no-pods.yml

+---
+title: Fix 500 error loading environments index
+merge_request: 31184
+author:
+type: fixed

ee/app/models/ee/clusters/platforms/kubernetes.rb

@@ -25,8 +25,7 @@ module EE
           project = environment.project
 
           deployments = filter_by_project_environment(data[:deployments], project.full_path_slug, environment.slug)
-          pods = filter_by_project_environment(data[:pods], project.full_path_slug, environment.slug) if data[:pods]&.any?
-
+          pods = filter_by_project_environment(data[:pods], project.full_path_slug, environment.slug)
           legacy_deployments = filter_by_legacy_label(data[:deployments], project.full_path_slug, environment.slug)
 
           ::Gitlab::Kubernetes::RolloutStatus.from_deployments(*deployments, pods: pods, legacy_deployments: legacy_deployments)

ee/spec/models/ee/clusters/platforms/kubernetes_spec.rb

@@ -67,6 +67,17 @@ describe Clusters::Platforms::Kubernetes do
         end
       end
 
+      context 'deployment with no pods' do
+        let(:deployment) { kube_deployment(name: 'some-deployment', environment_slug: environment.slug, project_slug: project.full_path_slug) }
+        let(:deployments) { [deployment] }
+        let(:pods) { [] }
+
+        it 'returns a valid status with matching deployments' do
+          expect(rollout_status).to be_kind_of(::Gitlab::Kubernetes::RolloutStatus)
+          expect(rollout_status.deployments.map(&:name)).to contain_exactly('some-deployment')
+        end
+      end
+
       context 'new deployment based on annotations' do
         let(:matched_deployment) { kube_deployment(name: 'matched-deployment', environment_slug: environment.slug, project_slug: project.full_path_slug) }
         let(:matched_pod) { kube_pod(environment_slug: environment.slug, project_slug: project.full_path_slug) }