Does a Collision in Space Affect a Spaceship's Center of Mass Motion?

[Count Iblis]

An object of mass m collides with a spaceship of mass M that is freely floating in intergalactic space. The mass was moving with a speed of v relative to the spacecraft and after the collision it sticks to the spaceship.

Estimate the probability that the collision won't affect the spaceship's center of mass motion at all.

 

[Redbelly98]

I would say the answer is obviously zero. So obviously I'm missing/misinterpreting something.