Fix C lint errors

[stdlib-bot]

C Linting Failures

Linting failures were detected in the automated lint workflow run.

Workflow Details

• Run: https://github.com/stdlib-js/stdlib/actions/runs/15033484298
• Type: C Linting
• Date: 2025-05-15 00:15:59 UTC

Error Details

lib/node_modules/@stdlib/stats/base/dmeanstdevpn/benchmark/c/benchmark.length.c:112:42: warning: Uninitialized variable: x [uninitvar]
  stdlib_strided_dmeanstdevpn( len, 1.0, x, 1, out, 1 );
                                         ^

Pull Request Instructions

• Please use the following PR title format:
  "chore: fix C lint errors (issue #<ISSUE_NUMBER>)".
• Reference this issue in the "Related Issues" section of the PR body as "resolves #<ISSUE_NUMBER>".