Inverse of 1x1 Matrix

[takfuruya]

$M([[2]]).inv()
returns the error:
TypeError: Cannot read property '1' of undefined
in Chrome developer tools inspector.

It should return a matrix of:
[[0.5]] instead.

[itamarwe]

Actually now it seems to work, there is even a test for this case in commit c01258a
Nevertheless, the code on the website (http://sylvester.jcoglan.com/) should probably be updated.