terraform: ResourceConfig.Get doesn't panic if exceed list bounds

[GH-210]

terraform/resource.go

@@ -149,6 +149,9 @@ func (c *ResourceConfig) get(
 				if err != nil {
 					return nil, false
 				}
+				if i >= int64(cv.Len()) {
+					return nil, false
+				}
 				current = cv.Index(int(i)).Interface()
 			}
 		default:

terraform/resource_test.go

@@ -55,6 +55,22 @@ func TestResourceConfigGet(t *testing.T) {
 			Key:   "foo",
 			Value: "bar",
 		},
+
+		{
+			Config: map[string]interface{}{
+				"foo": []interface{}{1, 2, 5},
+			},
+			Key:   "foo.0",
+			Value: 1,
+		},
+
+		{
+			Config: map[string]interface{}{
+				"foo": []interface{}{1, 2, 5},
+			},
+			Key:   "foo.5",
+			Value: nil,
+		},
 	}
 
 	for i, tc := range cases {