raise the threshold for mu0 in si_tchss to prevent division by 0

f90/cmo.f90

@@ -337,7 +337,7 @@ CONTAINS
     REAL(dp), INTENT(INOUT) :: RC
     REAL(dp), INTENT(IN) :: phin, zN
     REAL(dp) :: paravg, PARb, aim, depfrac, l1, l2
-    IF ((phy%PARs.GT.phy%I0).AND.(phy%mu0.GT.1E-30_dp)) THEN            ! (A4)
+    IF ((phy%PARs.GT.phy%I0).AND.(phy%mu0.GT.1E-10_dp)) THEN            ! (A4)
        PARb = MAX(phy%I0, phy%PARb)
        depfrac = LOG(phy%PARs/PARb)
        paravg = (phy%PARs - PARb)/depfrac