prevent float overflow when calculating He I population (#2522)

* prevent float overflow when calculating He I population

* reverse the change and raise error on T_rad instead

* delete extra )

* update the error message

* removing extra comma in text

* change value error to warning instead

* changed warning to logging.warn

* change to critical and capitalize TARDIS

tardis/model/parse_input.py

@@ -678,6 +678,13 @@ def parse_csvy_radiation_field_state(
             geometry, packet_source
         )
 
+    if np.any(t_radiative < 1000 * u.K):
+        logging.critical(
+            "Radiative temperature is too low in some of the shells, temperatures below 1000K "
+            f"(e.g., T_rad = {t_radiative[np.argmin(t_radiative)]} in shell {np.argmin(t_radiative)} in your model) "
+            "are not accurately handled by TARDIS.",
+        )
+
     if hasattr(csvy_model_data, "columns") and (
         "dilution_factor" in csvy_model_data.columns
     ):