Material doesn't have a texture property '_ShadowOffset'

I’m creating a tree in Unity and when I add the default branch texture it says “Material doesn’t have a texture property ‘_ShadowOffset’”. This is because the material doesn’t have the property ‘ShadowOffset’. In the inspector on the tree’s leaves and branch material they are missing 4 properties each: “Normalmap”, “Gloss (A)”, “Translucency (A)” and “Shadow Offset (A)”. How do I get these properties? This is for the BigTree prefab that comes with the Tree Creator Standard Assets pack.

I recommend having a look at this class:

It allows you to get a shader’s properties.