Fix #10385: Initialize directiveSubscriptions in music notes interaction directive

[kevintab95]

Overview

1. This PR fixes or fixes part of Music interaction doesn't work #10385.
2. This PR does the following:

• Initialize directiveSubscriptions in music notes interaction directive

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[oppiabot]

Assigning @aks681 for the first-pass review of this pull request. Thanks!

[vojtechjelinek]

LGTM from code owner's perspective. Thanks!

[oppiabot]

Hi @kevintab95. Due to recent changes in the "develop" branch, this PR now has a merge conflict. Please follow this link if you need help resolving the conflict, so that the PR can be merged. Thanks!

[kevintab95]

Looks like #10395 already fixed this. Thanks @orthodoxparadox!