optics_lib m_ice: short-wavelength branch search loop is a no-op ('continue' is not C continue), leading to out-of-bounds interpolation

[duncanwp]

Location: subsample_and_optics_example/optics/quickbeam_optics/optics_lib.F90, m_ice, line 542 (master 5eb05e5):

if (alam < cutice) then
   ! Region from 0.045 microns to 167.0 microns - no temperature depend
   do i=2,nwl
      if(alam < wl(i)) continue
   enddo
   x1  = log(wl(i-1))

In Fortran, continue is a no-op statement (not C's loop-continue), so this loop does nothing and always completes with i = nwl+1. The subsequent tabre(i) / wl(i) references then read one past the end of the nwl-sized arrays (silent out-of-bounds without -fcheck=bounds), and the interpolation uses the wrong bracket regardless.

The intended behaviour is clearly "find the first i with wl(i) > alam" (an exit instead of continue, or an infind-style search like the microwave branch below it).

Impact: latent for CloudSat use — at 94 GHz, alam = 3e5/94 ≈ 3191 um > cutice = 167 um, so only the temperature-dependent microwave branch executes. Any frequency above ~1.8 THz (or other reuse of m_ice at short wavelengths) would hit the broken branch.

Found while building a JAX translation of COSP (jax-cosp); its port implements the intended bracketing.