While it is quite true that in an ideal mathematical sense the eigenvectors of your matrix A ought to be linearly dependent, you must face the fact that you are using a computer which is subject to round-off errors because it has only a finite number of bits to represent its numbers. For that reason you obtained two vectors which are, strictly speaking, linearly independent because of a very tiny error.
Therefore in your code you must provide a tolerance for such tiny errors rather than expecting your computer to give you mathematically perfect results. This is entirely analogous to the computation .1+.2-.3 which doesn't yield an exact zero.
