Public Links are null for new questions

[oisincoveney]

Describe the bug

When trying to use the embed button + public link with new questions, the public link popover presents the user with a blank input box. When the user copies the link, the link comes out to

<INSTANCE URL>/api/card/null/public_link

We shouldn't allow users to share a public link until the question has been saved.

To Reproduce

1. Create a question (New → Question)
2. Click on the Share button (on the bottom right of the question view)
3. Click Create a public link
4. See that the link box is empty and copying the link gives a null URL

Expected behavior

We shouldn't allow users to share a public link until the question has been saved.

Logs

No response

Information about your Metabase installation

{
  "browser-info": {
    "language": "en-US",
    "platform": "MacIntel",
    "userAgent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/121.0.0.0 Safari/537.36",
    "vendor": "Google Inc."
  },
  "system-info": {
    "file.encoding": "UTF-8",
    "java.runtime.name": "OpenJDK Runtime Environment",
    "java.runtime.version": "21.0.2",
    "java.vendor": "Homebrew",
    "java.vendor.url": "https://github.com/Homebrew/homebrew-core/issues",
    "java.version": "21.0.2",
    "java.vm.name": "OpenJDK 64-Bit Server VM",
    "java.vm.version": "21.0.2",
    "os.name": "Mac OS X",
    "os.version": "14.1.1",
    "user.language": "en",
    "user.timezone": "Europe/Rome"
  },
  "metabase-info": {
    "databases": [
      "postgres",
      "h2"
    ],
    "hosting-env": "unknown",
    "application-database": "postgres",
    "application-database-details": {
      "database": {
        "name": "PostgreSQL",
        "version": "13.11"
      },
      "jdbc-driver": {
        "name": "PostgreSQL JDBC Driver",
        "version": "42.7.1"
      }
    },
    "run-mode": "dev",
    "version": {
      "date": "2024-01-29",
      "tag": "v1.48.1-SNAPSHOT",
      "hash": "1bb09a7"
    },
    "settings": {
      "report-timezone": null
    }
  }
}

Severity

P2

Additional context

No response