fix: allow undefined path in router resolve

[posva]

From #1904

Still need to check if we can avoid the path?: undefined in newer versions of TS.

[netlify]

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[codecov-commenter]

Codecov Report

Merging #1909 (962c4d2) into main (2e93d4b) will not change coverage.
The diff coverage is 100.00%.

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@@           Coverage Diff           @@
##             main    #1909   +/-   ##
=======================================
  Coverage   90.77%   90.77%           
=======================================
  Files          24       24           
  Lines        1117     1117           
  Branches      348      348           
=======================================
  Hits         1014     1014           
  Misses         63       63           
  Partials       40       40           

Impacted Files	Coverage Δ
packages/router/src/types/index.ts	100.00% <ø> (ø)
packages/router/src/errors.ts	91.66% <100.00%> (ø)
packages/router/src/matcher/index.ts	98.75% <100.00%> (ø)

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