refactor: remove unnecessary condition and add clarifying comment

Author: vkarpov15

lib/model.js

@@ -290,9 +290,10 @@ Model.prototype.$__handleSave = function(options, callback) {
 
   const session = this.$session();
   const asyncLocalStorage = this[modelDbSymbol].base.transactionAsyncLocalStorage?.getStore();
-  if (!saveOptions.hasOwnProperty('session') && session != null) {
+  if (session != null) {
     saveOptions.session = session;
   } else if (!options.hasOwnProperty('session') && asyncLocalStorage?.session != null) {
+    // Only set session from asyncLocalStorage if `session` option wasn't originally passed in options
     saveOptions.session = asyncLocalStorage.session;
   }
   if (this.$isNew) {