[yabridgectl] Gracefully catch bundle subdir error

This could only occur if people go out of their way to do weird things
and add the `x86_64-win` directory inside of a VST3 bundle to their
plugin locations. But somehow people still manage to do just that.....

CHANGELOG.md

@@ -6,6 +6,14 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic
 Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### yabridge
+
+- Don't panic when someone `yabridgectl add`'ed part of the contents of a
+  Windows VST3 bundle. For the record, you really, really, _really_ shouldn't be
+  doing this.
+
 ## [4.0.1] - 2022-06-12
 
 ### Added