allocate map if Labels is not initialized

pkg/kubectl/cmd/label.go

@@ -156,6 +156,10 @@ func labelFunc(obj runtime.Object, overwrite bool, resourceVersion string, label
 		}
 	}
 
+	if meta.Labels == nil {
+		meta.Labels = make(map[string]string)
+	}
+
 	for key, value := range labels {
 		meta.Labels[key] = value
 	}

pkg/kubectl/cmd/label_test.go

@@ -230,6 +230,17 @@ func TestLabelFunc(t *testing.T) {
 				},
 			},
 		},
+		{
+			obj: &api.Pod{
+				ObjectMeta: api.ObjectMeta{},
+			},
+			labels: map[string]string{"a": "b"},
+			expected: &api.Pod{
+				ObjectMeta: api.ObjectMeta{
+					Labels: map[string]string{"a": "b"},
+				},
+			},
+		},
 	}
 	for _, test := range tests {
 		out, err := labelFunc(test.obj, test.overwrite, test.version, test.labels, test.remove)