Transform in allow does not work properly when defined as null in deny

[darkship]

Hi,
In my repo https://github.com/darkship/test_allow_helpers, you will find that I defined transform : null in deny. It results that transforms aren't applyed to allow too.

Meteor-Community-Packages/meteor-collection2#144

[darkship]

Function Mongo.Collection.prototype._validatedUpdateLine 969 of packages/mongo/collection.js

Only the first transform is applied to the document. if (!factoriedDoc) should be removed twice.

[glasser]

Agree. Would review a PR with tests to fix this.