Pressing "Play" after closing Shader Forge window spams errors

After using Shader Forge for a while, producing a shader, and then closing the shader window (and going to other scenes and returning), whenever I press Play Shader forge throws out a bunch of errors: http://i.imgur.com/qUzXDRY.png

This is with the Shader Forge window closed - if I hit Window -> Shader Forge it brings me to the main menu that asks me to load a shader, etc. They might be leftover nodes in memory from the last shader I worked on?