Fixes https://github.com/denoland/deno/issues/28206.
Basically if you execute a script with `node:vm`, this produces a
"script" with the file name `evalmachine.<anonymous>`, which ends up
producing coverage like
```json
{
"scriptId": "319",
"url": "evalmachine.<anonymous>",
"functions": [
{
"functionName": "",
"ranges": [{ "startOffset": 0, "endOffset": 18, "count": 1 }],
"isBlockCoverage": true
}
]
}
```
We assume that the `url` field here (the specifier of the script) is a
valid URL, and so we error out when processing that coverage.
There are two potential fixes: either don't write the coverage files for
those scripts, or ignore the errors when we process the data. I went
with the former here.
Fixes #22941.
In that case, the only file with coverage was the `test.ts` file. The
coverage reporter filters out test files before compiling its report, so
after filtering we were left with an empty set of files. Later on it's
assumed that there is at least 1 file to be reported on, and we panic.
Instead of panicking, just issue an error after filtering.
