Also fixes (#131488)
Unreachable case is triggering `Callees.empty()` assert. Since this was
[originally
](02bd5a7013 (diff-06aba0dac2a263dc14297a15655291d5506b760f54a736385bcf3208f83df843R2524))
a `continue` anyway, have applied that as a fix and added a test case.
Please let me know if there's a better way.
Not sure who/how to get folks to review, tagging a few people (apologies
if you're not the right person/this is the wrong way to do it, please
let me know what to do in future if so)
@labrinea @dtcxzyw @nikic @fhahn
cc052667b4