Fix NonNull creation in Placeholder::new function

[djerry96]

Updated the creation of NonNull in the new function to avoid using an unstable feature.

Notes for Reviewer

Pre-Review Checklist for the PR Author

• PR title is short, expressive and meaningful
• Commits are properly organized
• Relevant issues are linked in the References section
• Tests are conducted
• Unit tests are added

Checklist for the PR Reviewer

• Commits are properly organized and messages are according to the guideline
• Unit tests have been written for new behavior
• Public API is documented
• PR title describes the changes

Post-review Checklist for the PR Author

• All open points are addressed and tracked via issues

References

Closes #

[github-actions]

License Check Results

🚀 The license check job ran with the Bazel command:

bazel run --lockfile_mode=error //:license-check

Status: ⚠️ Needs Review

Click to expand output

[License Check Output]
Extracting Bazel installation...
Starting local Bazel server (8.4.2) and connecting to it...
INFO: Invocation ID: 0e1a73b8-82aa-4cc1-ab49-7a9e73cfbf3c
Computing main repo mapping: 
WARNING: For repository 'rules_python', the root module requires module version rules_python@1.4.1, but got rules_python@1.8.3 in the resolved dependency graph. Please update the version in your MODULE.bazel or set --check_direct_dependencies=off
WARNING: For repository 'bazel_skylib', the root module requires module version bazel_skylib@1.7.1, but got bazel_skylib@1.8.2 in the resolved dependency graph. Please update the version in your MODULE.bazel or set --check_direct_dependencies=off
WARNING: For repository 'rules_cc', the root module requires module version rules_cc@0.1.1, but got rules_cc@0.2.14 in the resolved dependency graph. Please update the version in your MODULE.bazel or set --check_direct_dependencies=off
WARNING: For repository 'aspect_rules_lint', the root module requires module version aspect_rules_lint@2.0.0, but got aspect_rules_lint@2.3.0 in the resolved dependency graph. Please update the version in your MODULE.bazel or set --check_direct_dependencies=off
WARNING: For repository 'buildifier_prebuilt', the root module requires module version buildifier_prebuilt@7.3.1, but got buildifier_prebuilt@8.5.1 in the resolved dependency graph. Please update the version in your MODULE.bazel or set --check_direct_dependencies=off
Computing main repo mapping: 
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Analyzing: target //:license-check (142 packages loaded, 2717 targets configured)

Analyzing: target //:license-check (142 packages loaded, 2717 targets configured)

Analyzing: target //:license-check (152 packages loaded, 4981 targets configured)

Analyzing: target //:license-check (161 packages loaded, 8105 targets configured)

Analyzing: target //:license-check (164 packages loaded, 8123 targets configured)

Analyzing: target //:license-check (164 packages loaded, 8123 targets configured)

Analyzing: target //:license-check (164 packages loaded, 8123 targets configured)

Analyzing: target //:license-check (167 packages loaded, 10011 targets configured)

Analyzing: target //:license-check (168 packages loaded, 10135 targets configured)

Analyzing: target //:license-check (194 packages loaded, 10444 targets configured)
[10 / 17] JavaToolchainCompileClasses external/rules_java+/toolchains/platformclasspath_classes; 0s disk-cache, processwrapper-sandbox ... (2 actions, 1 running)
INFO: From Generating Dash formatted dependency file ...:
INFO: Successfully converted 5 packages from Cargo.lock to bazel-out/k8-fastbuild/bin/formatted.txt
Analyzing: target //:license-check (194 packages loaded, 10444 targets configured)
[15 / 17] JavaToolchainCompileBootClasspath external/rules_java+/toolchains/platformclasspath.jar; 0s disk-cache
Analyzing: target //:license-check (194 packages loaded, 10444 targets configured)
[16 / 17] [Prepa] Building license.check.license_check.jar ()
Analyzing: target //:license-check (194 packages loaded, 10444 targets configured)
[17 / 17] no actions running
Analyzing: target //:license-check (195 packages loaded, 10444 targets configured)
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INFO: Analyzed target //:license-check (195 packages loaded, 14778 targets configured).
INFO: Found 1 target...
Target //:license.check.license_check up-to-date:
  bazel-bin/license.check.license_check
  bazel-bin/license.check.license_check.jar
INFO: Elapsed time: 30.897s, Critical Path: 3.36s
INFO: 17 processes: 12 internal, 4 processwrapper-sandbox, 1 worker.
INFO: Build completed successfully, 17 total actions
INFO: Running command line: bazel-bin/license.check.license_check ./formatted.txt <args omitted>
usage: org.eclipse.dash.licenses.cli.Main [-batch <int>] [-cd <url>]
       [-confidence <int>] [-ef <url>] [-excludeSources <sources>] [-help] [-lic
       <url>] [-project <shortname>] [-repo <url>] [-review] [-summary <file>]
       [-timeout <seconds>] [-token <token>]

[github-actions]

The created documentation from the pull request is available at: docu-html

[pawelrutkaq]

its stable from 1.89 or ?