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

viper.go

@@ -757,11 +757,13 @@ 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:])
+				if val != nil {
 					jww.TRACE.Println(key, "found in nested config:", val)
 					return val
 				}
 			}
 		}
+	}
 
 	val, exists = v.kvstore[key]
 	if exists {