Do not allow aspect lock on disabled, but do allow nonsymmetric crop?

I honestly don't know which solution is better. HomeWorld fixed it by allowing aspect ratio lock based on its current size rather than its base size.

While this is inconsistent behaviour (normal aspect ratio lock jumps back to its base aspect ratio when you release shift after resizing something that is not in its base aspect, this does not).
At the same time, this could be called a feature: "Want to resize something and keep a custom aspect ratio? First resize without aspect lock. Disable the source and then resize with aspect lock. Then re-enable the source." Then again, that should probably be some other modifier, but I don't think we have any left.