phia: fix memory leak in findByKey()

Regression introduced by 335391d0

src/box/phia_index.cc

@@ -130,6 +130,9 @@ PhiaIndex::findByKey(struct phia_tuple *phia_key) const
 	if (result == NULL) /* not found */
 		return NULL;
 
+	auto tuple_guard = make_scoped_guard([=] {
+		phia_tuple_unref(db, result);
+	});
 	return phia_convert_tuple(db, result, key_def, format);
 }
 

test/phia/info.result

@@ -116,8 +116,8 @@ box_info_sort(box.info.phia())
     - cursor_read_disk: 0 0 0.0
     - delete: '0'
     - delete_latency: 0 0 0.0
-    - documents: '3'
-    - documents_used: '102'
+    - documents: '2'
+    - documents_used: '68'
     - get: '1'
     - get_latency: <get_latency>
     - get_read_cache: 0 0 0.0