this.world() returning null

**What would you like to achieve?**
I was debugging with the console when I saw the error:
```
Uncaught (in promise) TypeError: Cannot read properties of null (reading 'halos')
at DashboardControl.DashboardControl_slideIn_ (side-bar.cp.js:387:21)
```
The code was here:
```
$world.execCommand("open browser", {moduleName: "studio/side-bar.cp.js", packageName: "engageLively--galyleo-dashboard", codeEntity: "slideOut"});
```
And here:
```
$world.execCommand("open browser", {moduleName: "studio/side-bar.cp.js", packageName: "engageLively--galyleo-dashboard", codeEntity: "slideIn"});
```
The offending line was:
```
world.halos().forEach(h => h.maskBounds = world.getHaloMask());
```
`world` was null, and it had been set a few lines before with `world = this.world()`.
I fixed it by wrapping it in a null check, but I guess the author of the original code (@merryman ) thought that `this.world()` couldn't be `null`, so I wanted to check if there was a deeper issue.

**How are you trying to achieve that**

**Alternative solutions**
If applicable, what other solutions have you tried?

**Additional Resources**
Please provide links to any custom code that might be necessary to grasp your problem. Screenshots of custom component, etc. are also appreciated.

**Version**: Please paste the lively.next commit on which the problem occurred here (use the copy button of the Version Checker in the bottom left corner).
c725a776b26bd744331765a4881ba4c0557d2fea

Start with studio/side-bar.cp.js at the slideIn and slideOut code paths, especially where this.world() is assigned before world.halos(). Reproduce the null-world error at commit c725a776b26bd744331765a4881ba4c0557d2fea and inspect the surrounding world lifecycle. Done means the dashboard transition no longer dereferences a null world and its intended halo behavior remains intact.

Written by the indexing model from the issue text.