juliocamarero/liferay-portal — comment on commit a75cb1b639aa336779eed3b503a63428ebd39f46
File: portal-impl/src/com/liferay/portal/events/ServicePreAction.java line 538
By juliocamarero:

In order to make it backwards compatible and have an easy migration, for those sites with staging enabled and using a logo, after the upgrade they will have (logo=true logoId=0), and in this situation we will use the live logo.