Issue with dynamic segment in Middleware and NextConfig using trailingSlash: true

### Verify canary release - [X] I verified that the issue exists in the latest Next.js canary release ### Provide environment information ```bash Operating System: Platform: darwin Arch: arm64 Version: Darwin Kernel Version 23.0.0: Fri Sep 15 14:41:34 PDT 2023; root:xnu-10002.1.13~1/RELEASE_ARM64_T8103 Available memory (MB): 8192 Available CPU cores: 8 Binaries: Node: 20.12.2 npm: 10.5.0 Yarn: 1.22.22 pnpm: N/A Relevant Packages: next: 14.2.15 // Latest available version is detected (14.2.15). eslint-config-next: 14.2.15 react: 18.3.1 react-dom: 18.3.1 typescript: 5.6.3 Next.js Config: output: N/A ``` ### Which example does this report relate to? Custom Next.js configuration using middleware with trailingSlash: true and generateBuildId ### What browser are you using? (if relevant) Browser: Chrome 117.0.5938.132 ### How are you deploying your application? (if relevant) next start (local development) ### Describe the Bug I realized that when generateBuildId contains the character "/", for example, "release/example1", it will cause error. I hope this helps.  When using Next.js with the following configuration: `const nextConfig = { trailingSlash: true, generateBuildId: () => "release/v1", };` The initial page load at http://localhost:3000/product/1234/?Page=2 (with seriesCode being part of the dynamic route /product/[seriesCode]/?Page=2) works as expected, with seriesCode correctly set to 1234. However, when clicking a link that navigates to another product page such as http://localhost:3000/product/5678/?Page=2 from within the current page, the seriesCode is not passed or recognized, and only the Page=2 parameter is retained. ### Expected Behavior Upon navigating to a new product page with the format /product/[seriesCode]/?Page=[number], the seriesCode should be updated correctly with the new value. In this case, seriesCode should be 5678 when …