Why does my character model revert to a torso when I go into Pose mode to animate it? I rigged a model following some tutorials, and now I'm trying to make some basic animations.  I already know that my model is rigged properly, because I can get it to work using the motion captured animations pack in the Unity store.  However, following an example like this one, I go to put my model in pose mode, and I get this:

 

Instead of my full model to animate:



I'm sure this is something absolutely stupid that I'm missing, but I'd appreciate it if anyone can tell me why this is happening so that I can get back to work on this.  Learning things from tutorials is a great way to learn for free until something goes wrong that the tutorial doesn't expect.  My project is here.
The rigify addon creates an armature that uses drivers to control some parts of the rig. The leg bones have their scale calculated based on the value of the stretch_length, which is a custom property of the bone.

Blender has a security option that controls whether scripts are run automatically when opening a blend file, this includes drivers that use python expressions to define their calculations.

When you open a file with auto run scripts disabled these drivers aren't run so you end up with strange results like this.

The solution is to open the file with Trusted Source enabled or ensure it is in a path that is not listed as untrusted.