fix: guard against undefined options in source filtering

[hlfan]

Adds another guard to prevent #11532.

[k-yle]

this does fix the bug, but the proper solution would be to revert this manual change to the generated dist file.

source has "stringsCrossReference": "{source}" , which is circular reference, hence why field.options is undefined.

Since that edit is not in the main branch, there's probably no point in sending a PR. We'll need @tyrasd to update that file and make a new release

[tyrasd]

yeah, I had messed something up when creating the v6.13.3 dist release: I had an uncommitted test version of the source.json field in my directory which I though I had deleted, but wasn't. Sorry for that.

@hlfan I think there is still merit in merging this safeguard check. It could even come into play when people are running their own instance iD if nonstandard presets. Can you restore your branch, please?

[hlfan]

Nice to see the tests pass too now @tyrasd.