Fix 'flux get all --status-selector' for empty results

Signed-off-by: Matheus Pimenta <matheuscscp@gmail.com>

cmd/flux/testdata/get/kustomization_only.yaml

@@ -0,0 +1,26 @@
+---
+apiVersion: v1
+kind: Namespace
+metadata:
+  name: {{ .fluxns }}
+---
+apiVersion: kustomize.toolkit.fluxcd.io/v1
+kind: Kustomization
+metadata:
+  name: podinfo
+  namespace: {{ .fluxns }}
+spec:
+  interval: 5m
+  path: ./clusters/production
+  prune: true
+  sourceRef:
+    kind: GitRepository
+    name: podinfo
+status:
+  lastAppliedRevision: main@sha1:696f056df216eea4f9401adbee0ff744d4df390f
+  conditions:
+    - lastTransitionTime: "2021-08-01T04:52:56Z"
+      message: 'Applied revision: main@sha1:696f056df216eea4f9401adbee0ff744d4df390f'
+      reason: ReconciliationSucceeded
+      status: "True"
+      type: Ready