Dupe fix when finding default arg getters

Duplicate of i16814.

Author: dwijnand

tests/pos/i17008.scala

@@ -0,0 +1,9 @@
+abstract class A {
+  protected def foo(text: String, bar: () => Unit = () => ()): Unit = println(s"$text, $bar")
+}
+
+class B extends A {
+  def f1(): Unit = {
+    super.foo("X")
+  }
+}