set stage owner

src/main/java/org/cryptomator/ui/preferences/SupporterCertificateController.java

@@ -82,7 +82,8 @@ public class SupporterCertificateController implements FxController {
 
 	@FXML
 	void didClickRemoveCert() {
-		removeCert.build().showRemoveCert();
+		Stage pref = (Stage) supporterCertificateField.getScene().getWindow();
+		removeCert.build().showRemoveCert(pref);
 	}
 
 	public LicenseHolder getLicenseHolder() {

src/main/java/org/cryptomator/ui/removecert/RemoveCertComponent.java

@@ -18,10 +18,11 @@ public interface RemoveCertComponent {
 	@FxmlScene(FxmlFile.REMOVE_CERT)
 	Lazy<Scene> scene();
 
-	default void showRemoveCert() {
+	default void showRemoveCert(Stage owner) {
 		Stage stage = window();
 		stage.setScene(scene().get());
 		stage.sizeToScene();
+		stage.initOwner(owner);
 		stage.show();
 	}