add nil judge for dependency , maintainers validate and some testcase.

Signed-off-by: wujunwei <wjw3323@live.com>
(cherry picked from commit a7a1117327)

pkg/chart/dependency.go

@@ -53,6 +53,9 @@ type Dependency struct {
 // the chart. This check must be done at load time before the dependency's charts are
 // loaded.
 func (d *Dependency) Validate() error {
+	if d == nil {
+		return ValidationError("the dependency's item can not be nil")
+	}
 	d.Name = sanitizeString(d.Name)
 	d.Version = sanitizeString(d.Version)
 	d.Repository = sanitizeString(d.Repository)

pkg/chart/metadata.go

@@ -34,6 +34,9 @@ type Maintainer struct {
 
 // Validate checks valid data and sanitizes string characters.
 func (m *Maintainer) Validate() error {
+	if m == nil {
+		return ValidationError("the maintainer's item can not be nil")
+	}
 	m.Name = sanitizeString(m.Name)
 	m.Email = sanitizeString(m.Email)
 	m.URL = sanitizeString(m.URL)

pkg/chart/metadata_test.go

@@ -72,6 +72,30 @@ func TestValidate(t *testing.T) {
 			},
 			ValidationError("dependency \"bad\" has disallowed characters in the alias"),
 		},
+		{
+			&Metadata{
+				Name:       "test",
+				APIVersion: "v2",
+				Version:    "1.0",
+				Type:       "application",
+				Dependencies: []*Dependency{
+					nil,
+				},
+			},
+			ValidationError("the dependency's item can not be nil"),
+		},
+		{
+			&Metadata{
+				Name:       "test",
+				APIVersion: "v2",
+				Version:    "1.0",
+				Type:       "application",
+				Maintainers: []*Maintainer{
+					nil,
+				},
+			},
+			ValidationError("the maintainer's item can not be nil"),
+		},
 		{
 			&Metadata{APIVersion: "v2", Name: "test", Version: "1.2.3.4"},
 			ValidationError("chart.metadata.version \"1.2.3.4\" is invalid"),