The Canon EF-S 55-250mm f/4-5.6 IS STM is a light-weight lens made mostly of plastic. There should be no harm to your camera from the weight if you store it with the lens facing upwards. However, the LCD may be scratched if you happen to rest it on any grit.

There is risk of scratching the lens if you place it face down in the bag without a lens cap. The lens in question isn't sturdy enough to rest face down on a shelf while attached to a camera. (You can try, but don't be surprised if it falls over.)

Resting the camera with lens attached so that the lens is sideways, at an angle, with the front in contact with a surface, is usually an inefficient use of space. Leaving it that way on a shelf for long periods of time risks distortion to the mount or barrel. This may cause zoom to not work smoothly or other problems.

Consider what happens to cue sticks left leaning against walls. Lenses usually do not have this problem because they are able to stand vertically without support. However, if you leave one at an angle for long enough, I'd expect gravity would win.

Some bags have partitions you can use to store your camera with lens attached. Whatever position your bag is designed for should be safe for your camera and lens.