Copy-from limbs without explicit limb type / score definition crash while calculating manipulation score

### Describe the bug

The hardcoded manipulation score calc crashes when encountering a limb with copy-from that doesn't define/overwrite any limb type/scores.

### Attach save file

N/A

### Steps to reproduce

1. Remove the limb scores of any copy-from limb in the WIP limb mod (eg. bulging eyes)
2. Load up a game with the mod and mutate the modified trait
3. Check the @ menu encumbrance readout - the limb score of the eyes *will* be displayed correctly
4. Scroll to the mouth (the first item in the list with a manipulation score), behold crashage
5. Call stack shows manipulator score (via checking for aim speed)

### Expected behavior

Not crashing while copying-fromming

### Screenshots

_No response_

### Versions and configuration

Windows, compiled on master commit `d660a13f3a8555ce1b8c38f226afe77667ff6ff3`

### Additional context

Opened to help keep track of all weird lil limb breakage.

Reproduce the crash with a copy-from limb lacking explicit limb types or scores, then follow the call stack from the manipulator score calculation reached while checking aim speed. Verify the encumbrance readout still displays the eye score and no longer crashes when reaching the mouth or another limb with a manipulation score.

Written by the indexing model from the issue text.