Apply suggestions from code review

Co-authored-by: Matthew R. Becker <beckermr@users.noreply.github.com>

Author: beckermr

jax_galsim/core/utils.py

@@ -45,7 +45,7 @@ def check_is_int_then_cast(val, msg):
         if val != int(val):
             raise TypeError(msg)
         val = int(val)
-    else:
+    elif not has_tracers(val):
         # otherwise we use more opaque checking upon jit via equinox
         val = equinox.error_if(
             val,

jax_galsim/moffat.py

@@ -73,7 +73,7 @@ def __init__(
                 raise ValueError(
                     f"JAX-GalSim does not support Moffat beta values <= {self._beta_thr}."
                 )
-        else:
+        elif not has_tracers(beta):
             beta = equinox.error_if(
                 jnp.array(beta),
                 beta <= self._beta_thr,