ERROR_IF on invalid values in tensor shapes

Previously we were causing an internal error in allocation instead of
signlaling an ERROR in the graph.
Also fixes the shape given to the Eigen tensor used to represent shape_t
values of rank 0.

Signed-off-by: Ian Tayler Lessa <ian.taylerlessa@arm.com>
Signed-off-by: Peng Sun <peng.sun@arm.com>
Change-Id: I682fe0360b002b04af7b08e590d4f1acb4850d5c