Fix cppcheck warnings where array elements were accessed before validating
their indices. Reorder conditional expressions to ensure bounds checks are
performed before array accesses, taking advantage of C++ short-circuit
evaluation.
In EMNR::NP::interpM(), check the index limit before accessing xvals[idx].
In SNBA::scanFrame(), verify i is within the merit array bounds before
evaluating merit[i].
These changes improve defensive programming practices and prevent potential
undefined behavior if an index exceeds the valid range. No functional changes.
Signed-off-by: Robin Getz <rgetz503@gmail.com>