Extract link resolution into hrefAt and test image clicks

src/main/java/org/jabref/htmltonode/rich/RichTextRenderer.java

@@ -93,10 +93,7 @@ public static void configure(RichTextArea area, HtmlRenderOptions options) {
             if (event.getButton() == MouseButton.PRIMARY && event.isStillSincePress()) {
                 TextPos position = area.getTextPosition(event.getScreenX(), event.getScreenY());
                 if (position != null) {
-                    // Node segments (embedded images, tables) carry no character attributes, so the
-                    // model returns null there — only text runs can hold an HREF.
-                    StyleAttributeMap attributes = area.getModel().getStyleAttributeMap(null, position);
-                    String href = attributes != null ? attributes.get(HREF) : null;
+                    String href = hrefAt(area.getModel(), position);
                     if (href != null) {
                         options.linkHandler().accept(href);
                     }
@@ -105,6 +102,16 @@ public static void configure(RichTextArea area, HtmlRenderOptions options) {
         });
     }
 
+    /// Returns the link target at `position`, or `null` if there is none.
+    ///
+    /// Node segments (embedded images, tables) carry no character attributes, so the model
+    /// returns a null attribute map there — only text runs can hold an [#HREF]. Clicking an
+    /// image therefore lands on a null map, which this method tolerates.
+    public static @Nullable String hrefAt(StyledTextModel model, TextPos position) {
+        StyleAttributeMap attributes = model.getStyleAttributeMap(null, position);
+        return attributes != null ? attributes.get(HREF) : null;
+    }
+
     private void appendBlocks(List<Block> blocks) {
         for (Block block : blocks) {
             switch (block) {

src/test/java/org/jabref/htmltonode/RichTextRendererTest.java

@@ -142,6 +142,27 @@ void blockImageBecomesEmbeddedParagraph() {
         assertTrue(model.size() >= 2, "expected an embedded image paragraph before the text");
     }
 
+    @Test
+    void hrefAtImagePositionIsNullAndDoesNotThrow() {
+        // Clicking a book-cover / inline image resolves to a node segment, for which the model
+        // returns a null attribute map. hrefAt must tolerate that (regression for an NPE that
+        // dereferenced getStyleAttributeMap(...) on image clicks); offset 1 is the image node.
+        StyledTextModel model = model("a<img src=\"data:image/png;base64,"
+                + "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mP8z8BQDwAEhQGAhKmMIQAAAABJRU5ErkJggg==\">b");
+
+        assertEquals("a b", model.getPlainText(0));
+        assertNull(attributesAt(model, 0, 1), "image node segment carries no character attribute map");
+        assertNull(RichTextRenderer.hrefAt(model, TextPos.ofLeading(0, 1)));
+    }
+
+    @Test
+    void hrefAtLinkPositionReturnsTarget() {
+        StyledTextModel model = model("see <a href=\"https://doi.org/10.1/x\">10.1/x</a>");
+
+        assertEquals("https://doi.org/10.1/x", RichTextRenderer.hrefAt(model, TextPos.ofLeading(0, 5)));
+        assertNull(RichTextRenderer.hrefAt(model, TextPos.ofLeading(0, 1)));
+    }
+
     @Test
     void cslEntryRendersAsStyledCitation() {
         StyledTextModel model = model("""