[go_router] Fix: guard empty matches in _findCurrentNavigators and popRoute

[abhaysaqi]

When currentConfiguration.matches is empty (e.g. during startup before first route resolves), calling popRoute() crashed with 'Bad state: No element' from matches.last.

Added the same isEmpty guard that canPop() already uses, in both _findCurrentNavigators() and the popRoute() onExit fallback.

Fixes #187616

Replace this paragraph with a description of what this PR is changing or adding, and why. Consider including before/after screenshots.

List which issues are fixed by this PR. You must list at least one issue.

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[gemini-code-assist]

Code Review

This pull request adds checks to GoRouterDelegate to prevent 'Bad state: No element' errors when currentConfiguration is empty, along with a corresponding widget test. The review feedback suggests using the more idiomatic currentConfiguration.isEmpty instead of checking currentConfiguration.matches.isEmpty directly.

[stuartmorgan-g]

Thanks for the contribution! You’ve checked boxes in the PR checklist above that are not reflected in this PR, so I’m assuming this is a work in progress and am marking it as a Draft. Please review the checklist, updating the PR as appropriate, and when the state of the PR as posted reflects the checklist please feel free to mark it as ready for review.

[abhaysaqi]

Thanks for the contribution! You’ve checked boxes in the PR checklist above that are not reflected in this PR, so I’m assuming this is a work in progress and am marking it as a Draft. Please review the checklist, updating the PR as appropriate, and when the state of the PR as posted reflects the checklist please feel free to mark it as ready for review.

i don't know what i do now. could u share me with steps .i fixed issue and write fixed issue test case only.

[gemini-code-assist]

Code Review

This pull request introduces checks in GoRouterDelegate to handle cases where currentConfiguration or its matches are empty, preventing potential 'Bad state' exceptions, and adds a test to verify this behavior. The review feedback recommends using currentConfiguration.isEmpty instead of currentConfiguration.matches.isEmpty in the navigator states builder for consistency.

[abhaysaqi]

fixed issue

[stuartmorgan-g]

i don't know what i do now. could u share me with steps

That is what the checklist is: a set of steps you need to follow.

i fixed issue and write fixed issue test case only.

You need to do all of the steps in the checklist.

[abhaysaqi]

i don't know what i do now. could u share me with steps

That is what the checklist is: a set of steps you need to follow.

i fixed issue and write fixed issue test case only.

You need to do all of the steps in the checklist.

sure

[abhaysaqi]

All checklist items are now complete:

Updated PR title to start with [go_router]
Ran auto-formatter on changed files
Updated CHANGELOG.md with bug fix entry following repository style
Bumped version to 17.3.1 following semantic versioning (patch bump for bug fix)
Updated currentConfiguration.matches.isEmpty to currentConfiguration.isEmpty for consistency with the rest of the codebase
All 27 existing and new tests passing