additional check of length of experimental permittivity data > 0 (#242)

* added additional check if more than 0 permittivity points have been provided during creation of parameters

---------

Co-authored-by: LisaNeumaier <[email protected]>

src/epcsaft/parameters.rs

@@ -469,6 +469,21 @@ impl Parameter for ElectrolytePcSaftParameters {
             ));
         }
 
+        if !modeltypes.is_empty() && modeltypes[0] == 2 {
+            for permittivity_record in &permittivity_records {
+                if let Some(PermittivityRecord::ExperimentalData { data }) =
+                    permittivity_record.as_ref()
+                {
+                    // check if length of data is greater than 0
+                    if data.is_empty() {
+                        return Err(ParameterError::IncompatibleParameters(
+                                "Experimental data for permittivity must contain at least one data point.".to_string(),
+                            ));
+                    }
+                }
+            }
+        }
+
         if !modeltypes.is_empty() && modeltypes[0] == 2 {
             // order points in data by increasing temperature
             let mut permittivity_records_clone = permittivity_records.clone();