support fromLinking in subtypes too (with test confirming the problem),

phetsims/tandem#300

Signed-off-by: Michael Kauzmann <[email protected]>

js/ReadOnlyProperty.ts

@@ -627,17 +627,17 @@ export default class ReadOnlyProperty<T> extends PhetioObject implements TReadOn
   /**
    * Support treating ourselves as an autoselectable entity for the "strings" selection mode.
    */
-  public override getPhetioMouseHitTarget(): PhetioObject | 'phetioNotSelectable' {
+  public override getPhetioMouseHitTarget( fromLinking = false ): PhetioObject | 'phetioNotSelectable' {
 
     if ( phet.tandem.phetioElementSelectionProperty.value === 'string' ) {
 
       // As of this writing, the only way to get to this function is for Properties that have a value of strings, but
       // in the future that may not be the case. SR and MK still think it is preferable to keep this general, as false
       // positives for autoselect are generally better than false negatives.
-        return this.getPhetioMouseHitTargetSelf();
+      return this.getPhetioMouseHitTargetSelf();
     }
 
-    return super.getPhetioMouseHitTarget();
+    return super.getPhetioMouseHitTarget( fromLinking );
   }