Asset reference points to a Blueprint that no longer exists

Why: Some node or variable hardcoded a reference to BP_{name}, but that file was deleted or moved. The Asset Registry can't resolve it.

Fix: Either: (a) re-create BP_{name} if accidentally deleted (Content Browser → right-click → Blueprint Class), or (b) update the reference to point at the correct existing Blueprint, or (c) make the reference soft (TSoftObjectPtr) so missing assets don't fail compilation.