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

viper.go

@@ -802,8 +802,10 @@ 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

@@ -907,3 +907,12 @@ func TestSetConfigNameClearsFileCache(t *testing.T) {
 	SetConfigName("default")
 	assert.Empty(t, v.getConfigFile())
 }
+
+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)
+}