Normal maps in skinned/rigged meshes fail to work correctly

[TwistedTwigleg]

Operating system or device - Godot version:
Linux 64-bit (Ubuntu 16.04 LTS) Godot version 3.0 (daily build May 2)

Issue description:

Assigning a normal map to a Spatial Material causes the mesh to become white and massively scaled up. It only seems to work for meshes that have a skeleton, even if the skeleton is empty. Normal maps work fine on the mesh if it doesn't have a skeleton.

Steps to reproduce:
Import a rigged model and assign a normal map to it's Spatial Material.

Link to minimal example project:

Example project attached. (Cannot provide textures though, sorry! I used textures from Free PBR)
Example_project.zip