Fixed clang analyzer warning about reading uninitialized data.

If 'nmat' is not positive, 'inputsPerMaterial' becomes meaningless but is used anyway,
bail early if so.

Also replaced ISO-8859 'squared' character with ASCII "^2",
since it was confusing my text editor and git diff.

Change-Id: I480447340a2ff541453eddce8c090d8e31e2a01a