fix panic when fieldspec refers an empty value

api/krusty/namereference_test.go

@@ -0,0 +1,44 @@
+package krusty_test
+
+import (
+	"testing"
+
+	kusttest_test "sigs.k8s.io/kustomize/api/testutils/kusttest"
+)
+
+func TestEmptyFielsSpecValue(t *testing.T) {
+	th := kusttest_test.MakeHarness(t)
+	th.WriteK("/app", `
+generators:
+- generators.yaml
+configurations:
+- kustomizeconfig.yaml
+`)
+	th.WriteF("/app/generators.yaml", `
+apiVersion: builtin
+kind: ConfigMapGenerator
+metadata:
+  name: secret-example
+labels:
+  app.kubernetes.io/name: secret-example
+literals:
+- this_is_a_secret_name=
+`)
+	th.WriteF("/app/kustomizeconfig.yaml", `
+nameReference:
+- kind: Secret
+  version: v1
+  fieldSpecs:
+  - path: data/this_is_a_secret_name
+    kind: ConfigMap
+`)
+	m := th.Run("/app", th.MakeDefaultOptions())
+	th.AssertActualEqualsExpected(m, `
+apiVersion: v1
+data:
+  this_is_a_secret_name: ""
+kind: ConfigMap
+metadata:
+  name: secret-example-7hf4fh868h
+`)
+}