Don't assume attributes passed to find are actually model attributes

lib/model.js

@@ -1726,7 +1726,7 @@ module.exports = (function() {
         // Object lookups will force any variable to strings, we don't want that for special objects etc
         if (typeof attr !== "string") return attr;
         // Map attributes to aliased syntax attributes
-        if (attr !== Model.rawAttributes[attr].field) {
+        if (Model.rawAttributes[attr] && attr !== Model.rawAttributes[attr].field) {
           return [Model.rawAttributes[attr].field, attr];
         }
         return attr;