dont post open wallets event until scene set

src/main/java/com/sparrowwallet/sparrow/transaction/HeadersController.java

@@ -420,12 +420,20 @@ public class HeadersController extends TransactionFormController implements Init
                 signaturesProgressBar.initialize(headersForm.getSignatureKeystoreMap(), threshold);
             });
 
-            Platform.runLater(() -> EventManager.get().post(new RequestOpenWalletsEvent()));
+            Platform.runLater(this::requestOpenWallets);
         }
 
         blockchainForm.setDynamicUpdate(this);
     }
 
+    private void requestOpenWallets() {
+        if(id.getScene() != null) {
+            EventManager.get().post(new RequestOpenWalletsEvent());
+        } else {
+            Platform.runLater(this::requestOpenWallets);
+        }
+    }
+
     private void updateType() {
         String type = "Legacy";
         if(headersForm.getTransaction().isSegwit() || (headersForm.getPsbt() != null && headersForm.getPsbt().getPsbtInputs().stream().anyMatch(in -> in.getWitnessUtxo() != null))) {