Code blocks inside .. collapse:: directives are sometimes displayed without text

[DSSAtDatagen]

Describe the bug

context
I place thebe code blocks inside .. collapse:: directives on a regular basis.

expectation
I expect the code block to act the same way as any other code block.

bug
But instead - and on Firefox browsers only - the input section of the code block has no text in it.

This only happens if the kernel is activated before you open the collapsed section of the page. And it only happens on Firefox; it does not happen on Edge or Chrome

Reproduce the bug

1. Create a ..collapse:: directive and put a thebe-enabled .. code-block:: inside of it.
2. Build
3. Open the page in Firefox 108.0.2 (the latest version, though this has been an issue for some time)
4. Activate the kernel
5. Open the collapse directive
6. Notice that the input block is blank.
7. Click in the input block and the text that should be there suddenly appears.

Example of a blank input block that actually has text in it:

List your environment

I'm using Firefox 108.0.2 on Windows 10.

sphinx-thebe: 0.1.2
myst-parser: 0.15.2
sphinx: 4.5.0
docutils: 0.17.1

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