message: Actually set the program uniform
diff: @@ -787,6 +787,10 @@ fn bind_image_uniform<P, T>(
  None => return Err(DrawError::InsufficientImageUnits),
  };
  + // Update the program to use the right unit
  + program.set_uniform(ctxt, location,
  + &RawUniformValue::SignedInt(image_unit as gl::types::GLint));
  +
  let (layered, layer) = match unit_behavior.layer {
  None => (false, 0),
  Some(l) => (true, l)
  