huh, it broke?

So I was creating a mod that adds new utilities to the game, one being a purifier. Basically, you find generated oily stone (mine to get 3 oily rocks) and use that to make Calcium. then put that in a crafting table (or something) with milk and you get purified milk (which would give hearts). While making the Purified Milk itself, I was going to make a texture for it. Then the box showed up but it was blank and looked like a Mac window instead of MCreator's window. I couldn't close it, when I pressed CMD + Q it didn't close, and the only way I could close it was by force quitting. 

And all I wanted was to make a texture.

Please patch this, I do not know why this happens, but it does.