Allow empty document to be deserialized using visit_none

src/de.rs

@@ -1247,7 +1247,7 @@ impl<'de, 'document> de::Deserializer<'de> for &mut DeserializerFromEvents<'de,
                 }
                 Event::SequenceEnd => panic!("unexpected end of sequence"),
                 Event::MappingEnd => panic!("unexpected end of mapping"),
-                Event::Void => break Err(error::new(ErrorImpl::EndOfStream)),
+                Event::Void => break visitor.visit_none(),
             }
         }
         // The de::Error impl creates errors with unknown line and column. Fill

tests/test_de.rs

@@ -559,6 +559,10 @@ fn test_no_required_fields() {
         let expected = None;
         let deserialized: Option<String> = serde_yaml::from_str(document).unwrap();
         assert_eq!(expected, deserialized);
+
+        let expected = Value::Null;
+        let deserialized: Value = serde_yaml::from_str(document).unwrap();
+        assert_eq!(expected, deserialized);
     }
 }