Fix a message about an undefined setting

[nigredo-tori]

defining seems to be a setting or a task that references referencedKey, not the other way around.

[eed3si9n]

I just confirmed this using the following.

steps

ThisBuild / scalaVersion     := "2.13.1"
ThisBuild / version          := "0.1.0-SNAPSHOT"
ThisBuild / organization     := "com.example"
ThisBuild / organizationName := "example"

lazy val foo = settingKey[String]("")
lazy val bar = taskKey[String]("")

lazy val root = (project in file("."))
  .settings(
    name := "hello",
    bar := (Def.taskDyn {
      Def.task { foo.value }
    }).value
  )

sbt:hello> bar

problem

sbt:hello> bar
[error] stack trace is suppressed; run last bar for the full output
[error] (bar) sbt.internal.util.Init$RuntimeUndefined: References to undefined settings at runtime.
[error] setting(ScopedKey(Scope(Select(ProjectRef(file:/private/tmp/hello/,root)), Zero, Zero, Zero),bar)) at LinePosition(/private/tmp/hello/build.sbt,14) referenced from ScopedKey(Scope(Select(ProjectRef(file:/private/tmp/hello/,root)), Zero, Zero, Zero),foo)

expectation

sbt:hello> bar
[error] stack trace is suppressed; run last bar for the full output
[error] (bar) sbt.internal.util.Init$RuntimeUndefined: References to undefined settings at runtime.
[error] ScopedKey(Scope(Select(ProjectRef(file:/private/tmp/hello/,root)), Zero, Zero, Zero),foo) at LinePosition(/private/tmp/hello/build.sbt,14) referenced from setting(ScopedKey(Scope(Select(ProjectRef(file:/private/tmp/hello/,root)), Zero, Zero, Zero),bar))

[eed3si9n]

Thanks for the contribution!