[R]: check the input of fm.eigen.
[R]: check the input of fm.eigen.

We have to make sure the eigensolver doesn't crash when giving an
invalud input.

flashxio/FlashX,flashxio/FlashX,flashxio/FlashX,flashxio/FlashX,icoming/FlashX,flashxio/FlashX,icoming/FlashX,flashxio/FlashX,icoming/FlashX,icoming/FlashX,icoming/FlashX