Applying a theme causes a flood of exceptions in the developer console.

[okets]

My Home Assistant version: 2025.1.2

My lovelace configuration method (GUI or yaml): YAML & GUI

What I am doing: Change themes programmatically in one of my custom cards

What I expected to happen:
not to spam the console with errors.
What happened instead:
the console is spammed with errors.

Minimal steps to reproduce:
change the theme dynamically using a button that calls "setTheme"
this is a code for the button:

const ev = new Event("settheme", {
	bubbles: true,
	cancelable: false,
	composed: true,
});
ev.detail = { theme: "my-theme" }
this.dispatchEvent(ev);

# The least amount of code possible to reproduce my error
The problem has nothing to do with YAML, it happens whenever the theme is changed programmatically.
# End of code

Error messages from the browser console:
Uncaught (in promise) SyntaxError: "undefined" is not valid JSON
I have debugged it and figured out the source of the error.
in the constructor you call:

document.addEventListener("cm_update", () => {
    this._process_styles(this.card_mod_input);
});

in order to prevent this bug, I capture the event myself and stopPropagation so your event listener will not pop.

the bug occurs even after removing all card_mod instructions, just having card-mod installed and changing themes dynamically is enough.

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