Mesa is a GL renderer. POT only matters in 3D for things like texture sizes. Textures aren't allowed to have zero-sized dimensions. The check for v == 0 occurs

Mesa is a GL renderer. POT only matters in 3D for things like texture sizes. Textures aren't allowed to have zero-sized dimensions. The check for v == 0 occurs far higher up the stack than where this function's used. We're not writing bad code, we promise. :3