bug(getwherecond) Fix a bug where passing null as the second parameter to would fail Closes #4334

changelog.md

 # Next
 - [FIXED] Fall back to a default version when parsing the DB version fails [#4368](https://github.com/sequelize/sequelize/issues/4368)
+- [FIXED] Fix a bug where passing null as the second parameter to `sequelize.where` would fail [#4334](https://github.com/sequelize/sequelize/issues/4334)
 
 # 3.6.0
 - [ADDED] Model.findCreateFind: A more performant findOrCreate that will not work under a transaction (atleast not in postgres)

lib/dialects/abstract/query-generator.js

@@ -1708,7 +1708,7 @@ var QueryGenerator = {
         key = this.quoteTable(smth.attribute.Model.name) + '.' + this.quoteIdentifier(smth.attribute.field || smth.attribute.fieldName);
       }
 
-      if (value._isSequelizeMethod) {
+      if (value && value._isSequelizeMethod) {
         value = this.getWhereConditions(value, tableName, factory, options, prepend);
 
         result = (value === 'NULL') ? key + ' IS NULL' : [key, value].join(smth.comparator);

test/unit/sql/where.test.js

@@ -682,4 +682,18 @@ suite(Support.getTestDialectTeaser('SQL'), function() {
       });
     });
   });
+
+  suite('getWhereConditions', function () {
+    var testsql = function (value, expectation) {
+      var User = current.define('user', {});
+
+      test(util.inspect(value, {depth: 10}), function () {
+        return expectsql(sql.getWhereConditions(value, User.tableName, User), expectation);
+      });
+    };
+
+    testsql(current.where(current.fn('lower', current.col('name')), null), {
+      default: "lower([name]) IS NULL"
+    });
+  });
 });