A couple of days ago someone posted the same thing on the forums. From what I gather it’s not specific to the blank app. But it depends on what mendix version you start the app or template in. When creating an app in 7.13 or lower they could create it on the specific version number. But if you tried it with something like 7.23.x (and some versions lower than that) it always created an app for 7.23.4.
Not exactly sure where the cutoff point is for this behavior though. Or why. If it’s a bug or a design choice by Mendix.
I started up mendix modeler 7.7.1. Clicked on new app and then blank app. It starts to generate a version and upon completion has created a blank app for version 7.7.1.
I don't run into this message, maybe try from a modeler?