Arrays with weird indices break show_array2d_bool

[wldhx]

Hi, here's a repro:

array[0..2,0..2] of var bool: occupancy;
output show_array2d_bool(occupancy);

Yields

Error: evaluation error: overflow in floating point operation

Switching indices to 1..2 fixes it.

> minizinc --version                 
MiniZinc to FlatZinc converter, version 2.8.2
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