correctly checks the storage in ToyAccount (#7214)

Signed-off-by: Karim Taam <karim.t2am@gmail.com>

evm/src/test/java/org/hyperledger/besu/evm/toy/ToyAccount.java

@@ -171,7 +171,10 @@ public class ToyAccount implements MutableAccount {
    */
   @Override
   public boolean isStorageEmpty() {
-    return storage.isEmpty();
+    if (storage.isEmpty()) {
+      return parent == null || parent.isStorageEmpty();
+    }
+    return false;
   }
 
   @Override