If this error is displayed, it means your computer doesn't support shaders. One possibility could be that you don't have the DirectX 9 runtime installed, you should be able to get it from here: https://www.microsoft.com/en-us/download/details.aspx?displaylang=en&id=35
If that fails, the problem is probably that your GPU doesn't support OpenGL, and you'll need to remove the shader from the game (and remove the code in parent_enemy that sets and resets the shader before drawing, so you don't have a reference to a nonexistent resource).