ROC of z transform of u(-n+1)
Since 

\$|z| = 0 ~~\Leftrightarrow~~ z = 0 \$ 

for z = 0 you cannot compute the term outside the sum symbol, i.e. \$z^{-1}\$, which is part of your transform. In other words, for \$z = 0\$ the transform does not exist.

Maybe you were put off-tracks because \$|z|\ge 0\$ by definition, but now you have to exclude \$ |z| = 0 \$ from the interval of valid values of \$|z|\$.