fix(tanstack-router): Check for `fromLocation` existence before reporting pageload

[github-actions]

Note

The pull request "fix(tanstack-router): Check for fromLocation existence before reporting pageload" was created by @logaretm but did not reference an issue. Therefore this issue was created for better visibility in external tools like Linear.

Bad condition which short circuits the web vitals from being reported, I included a test anyways even thought it doesn't reproduce it.

[linear]

JS-1288

[logaretm]

duplicate of #18425 😠