Fix no initial title consuming events.

src/book/summary.rs

@@ -536,6 +536,10 @@ impl<'a> SummaryParser<'a> {
                 // Skip a HTML element such as a comment line.
                 Some(Event::Html(_)) => {}
                 // Otherwise, no title.
+                Some(ev) => {
+                    self.back(ev);
+                    return None;
+                }
                 _ => return None,
             }
         }
@@ -647,6 +651,15 @@ mod tests {
         assert_eq!(got, should_be);
     }
 
+    #[test]
+    fn no_initial_title() {
+        let src = "[Link]()";
+        let mut parser = SummaryParser::new(src);
+
+        assert!(parser.parse_title().is_none());
+        assert!(matches!(parser.next_event(), Some(Event::Start(Tag::Paragraph))));
+    }
+
     #[test]
     fn parse_title_with_styling() {
         let src = "# My **Awesome** Summary";