Fix storage engine bug for zero-sized map entries

gt was applicable here instead of ge, since for zero-sized elements, we
may have already reached the end of allocation.

server/src/storage/mod.rs

@@ -409,7 +409,7 @@ mod de {
                 // this is what we have left: [KLEN:8B][VLEN:8B]
                 let end_ptr = data.as_ptr().add(data.len());
                 for _ in 0..len {
-                    if (ptr.add(16)) >= end_ptr {
+                    if (ptr.add(16)) > end_ptr {
                         // not enough space
                         return None;
                     }

server/src/storage/tests.rs

@@ -34,6 +34,19 @@ fn test_serialize_deserialize_empty() {
     assert!(de.len() == 0);
 }
 
+#[test]
+fn test_serialize_deserialize_map_with_empty_elements() {
+    let cmap = Coremap::new();
+    cmap.true_if_insert(Data::from("sayan"), Data::from(""));
+    cmap.true_if_insert(Data::from("sayan's second key"), Data::from(""));
+    cmap.true_if_insert(Data::from("sayan's third key"), Data::from(""));
+    cmap.true_if_insert(Data::from(""), Data::from(""));
+    let ser = se::serialize_map(&cmap).unwrap();
+    let de = de::deserialize_map(ser).unwrap();
+    assert_eq!(de.len(), cmap.len());
+    assert!(cmap.into_iter().all(|(k, v)| de.get(&k).unwrap().eq(&v)));
+}
+
 #[test]
 fn test_ser_de_few_elements() {
     let cmap = Coremap::new();