Prevent shadowning of keys when a nested key's value is nil.

viper.go

@@ -788,8 +788,10 @@ func (v *Viper) find(key string) interface{} {
 		if source != nil {
 			if reflect.TypeOf(source).Kind() == reflect.Map {
 				val := v.searchMap(cast.ToStringMap(source), path[1:])
-				jww.TRACE.Println(key, "found in nested config:", val)
-				return val
+				if val != nil {
+					jww.TRACE.Println(key, "found in nested config:", val)
+					return val
+				}
 			}
 		}
 	}

viper_test.go

@@ -883,3 +883,12 @@ func TestUnmarshalingWithAliases(t *testing.T) {
 
 	assert.Equal(t, &C, &config{Id: 1, FirstName: "Steve", Surname: "Owen"})
 }
+
+func TestShadowedNestedValue(t *testing.T) {
+	polyester := "polyester"
+	initYAML()
+	SetDefault("clothing.shirt", polyester)
+
+	assert.Equal(t, GetString("clothing.jacket"), "leather")
+	assert.Equal(t, GetString("clothing.shirt"), polyester)
+}