fix: reject wildcard array that compiles to an empty path

[spokodev]

compile for a wildcard accepts an array whose only content is empty, and silently returns a path the same pattern can never match:

compile("/*foo")({ foo: [""] }); //=> "/"
match("/*foo")("/");             //=> false

The value is lost with no error. This is the array counterpart of the empty-string param case rejected in #444.

A wildcard's value domain is exactly what match produces — capturedValue.split(delimiter) — and match can never yield [""], since the capture group requires at least one character. So there is no input for which [""] is a correct value; compile should reject it rather than emit an unmatchable path.

The fix throws when the joined output is empty. Arrays that contain empty segments but still produce content (e.g. ["a", ""] → "/a/", ["route", "nested", ""] → "/route/nested/") are what match returns for trailing/empty segments and continue to round-trip unchanged.

Adds a regression test.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.75%. Comparing base (c83a925) to head (5a7a44d).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #448   +/-   ##
=======================================
  Coverage   99.75%   99.75%           
=======================================
  Files           1        1           
  Lines         400      403    +3     
  Branches      161      163    +2     
=======================================
+ Hits          399      402    +3     
  Misses          1        1           

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