EPUB Input: Handle ncx files that have <navpoint> elements with no content correctly. Fixes #7396 (calibre does not show TOC from attached epub file)

src/calibre/ebooks/metadata/toc.py

@@ -182,6 +182,7 @@ class TOC(list):
             except:
                 play_order = 1
             href = fragment = text = None
+            nd = dest
             nl = nl_path(np)
             if nl:
                 nl = nl[0]
@@ -190,13 +191,10 @@ class TOC(list):
                     text += etree.tostring(txt, method='text',
                             encoding=unicode, with_tail=False)
                 content = content_path(np)
-                if not content or not text:
-                    return
+                if content and text:
                     content = content[0]
                     src = get_attr(content, attr='src')
-                if src is None:
-                    return
-
+                    if src:
                         purl = urlparse(unquote(content.get('src')))
                         href, fragment = purl[2], purl[5]
                         nd = dest.add_item(href, fragment, text)

src/calibre/gui2/viewer/main.py

@@ -358,6 +358,7 @@ class EbookViewer(MainWindow, Ui_EbookViewer):
 
     def toc_clicked(self, index):
         item = self.toc_model.itemFromIndex(index)
+        if item.abspath is not None:
             url = QUrl.fromLocalFile(item.abspath)
             if item.fragment:
                 url.setFragment(item.fragment)