_onResize method called before stage initialization

[BeNikk]

Description

The _onResize method in activity.js is being called before this.stage is properly initialized, which could lead to potential errors during the application startup. This occurs during the initial loading phase of Music Blocks.

Expected Behavior

The _onResize method should only execute its resize operations after this.stage has been properly initialized. Currently, we've added a defensive check, but the root cause of the early resize call should be investigated.

Screenshots

How to Reproduce

1. Load Music Blocks in browser
2. Open browser developer tools
3. Observe that _onResize is called during initialization
4. Check the timing of this.stage initialization versus the first resize call

Environment:

• Operating System: All (This is a core initialization issue)
• Browser: All modern browsers
• Version of Software/Project: Current main branch

Checklist

• I have read and followed the project's code of conduct.
• I have searched for similar issues before creating this one.
• I have provided all the necessary information to understand and reproduce the issue.
• I am willing to contribute to the resolution of this issue.

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