Link to a tag rather than to master.

Author: armiol

release-notes/2019/v1.2.0.md

@@ -16,7 +16,7 @@ This release includes several new features and some existing feature improvement
 
 - The [client](https://github.com/SpineEventEngine/dart) based on [Dart](https://dart.dev/) 
 programming language is now available. The `base` is extended with Dart-related 
-[tools]({{site.base_repo}}/tree/master/tools/proto-dart-plugin).
+[tools]({{site.base_repo}}/tree/v1.2.0/tools/proto-dart-plugin).
 - Several API improvements for precondition checks ([#486]({{site.base_repo}}/pull/486), 
 [#487]({{site.base_repo}}/pull/487)).
 - It is now allowed to disable the validating builders generation when using Spine Model