Fix some compiler warnings in the renderer

[sebholt]

Pull Request Type

• GitHub Workflow changes
• Documentation or Wiki changes
• Build and Dependency changes
• Runtime changes
  • Render changes
  • Audio changes
  • Input changes
  • Network changes
  • Other changes

Description

In the renderer this fixes some compiler warnings and replaces mem_malloc with mem_rmalloc.

Related Issues

Screenshots (if applicable)

Checklist

• I have tested my changes locally and verified that they work as intended.
• I have documented any new or modified functionality.
• I have reviewed the changes to ensure they do not introduce any unnecessary complexity or duplicate code.
• I understand that by submitting this pull request, I am agreeing to license my contributions under the project's license.

Additional Comments

[Lgt2x]

Looks good, thanks. While it's obvious here, you could specify what exact warning is fixed in your commit messages.