From 7d279cf2c9aef0c1fb55d4b945bad8fda4720dc6 Mon Sep 17 00:00:00 2001
From: Carl Christian Snethlage <cc.snethlage@gmail.com>
Date: Mon, 3 Jan 2022 23:57:48 +0100
Subject: [PATCH] quickfix

---
 src/main/java/org/jabref/gui/theme/ThemeManager.java | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/src/main/java/org/jabref/gui/theme/ThemeManager.java b/src/main/java/org/jabref/gui/theme/ThemeManager.java
index 7b1e9829e0e..f317891282e 100644
--- a/src/main/java/org/jabref/gui/theme/ThemeManager.java
+++ b/src/main/java/org/jabref/gui/theme/ThemeManager.java
@@ -1,6 +1,7 @@
 package org.jabref.gui.theme;
 
 import java.io.IOException;
+import java.net.URL;
 import java.nio.file.Path;
 import java.util.Collections;
 import java.util.List;
@@ -160,7 +161,14 @@ private void updateAdditionalCss(Scene scene) {
         scene.getStylesheets().setAll(List.of(
                 baseStyleSheet.getSceneStylesheet().toExternalForm(),
                 appearancePreferences.getTheme()
-                                     .getAdditionalStylesheet().map(styleSheet -> styleSheet.getSceneStylesheet().toExternalForm())
+                                     .getAdditionalStylesheet().map(styleSheet -> {
+                                         URL stylesheetUrl = styleSheet.getSceneStylesheet();
+                                         if (stylesheetUrl != null) {
+                                             return stylesheetUrl.toExternalForm();
+                                         } else {
+                                             return "";
+                                         }
+                                     })
                                      .orElse("")
         ));
     }